[BUG] WeightRegression produces incorrect regression when thru_orig = False #1024

Open
Bug
Open
[BUG] WeightRegression produces incorrect regression when thru_orig = False#1024
Bug
Assignees
henrydingliu
Labels
Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!

Description

@henrydingliu
henrydingliu
opened on Jun 19, 2026

Are you on the latest chainladder version?

  • Yes, this bug occurs on the latest version.

Describe the bug in words

came across a bug in _fit_OLS while trying to recreate chapter 11. likely culprit is a missing w (or two) around here. should be a quick PR for the students in our contributor group

How can the bug be reproduced?

test=cl.Triangle(
data= {
'value':[100,200,300,400,500,0,0,0],
'weight':[1,1,1,1,1,0,0,0],
'ay': [2001,2002,2003,2004,2005,2006,2007,2008],
'dev':[2008,2008,2008,2008,2008,2008,2008,2008],
},
origin='ay',
development='dev',
columns=['value','weight'],
cumulative=True,
)
reg=cl.WeightedRegression(
axis=2,
thru_orig=False,
xp=test.get_array_module()
).fit(
np.ones((1,1,8,1)) *test.origin.year.values[None,None,:,None],
test['value'].values,
test['weight'].values
)
reg.slope_

What is the expected behavior?

100

Would you be willing to contribute this ticket?

  • Yes, absolutely!
  • Yes, but I would like some help.
  • No.

Metadata

Metadata

Assignees

Labels

Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!

Type

Bug

Fields

Priority

Urgent

Effort

Low

Scope

Codebase

Projects

Milestone

No milestone

Relationships

None yet

Development

No branches or pull requests

Issue actions

, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

Skip to content
[BUG] WeightRegression produces incorrect regression when thru_orig = False #1024
Open
Bug
Open
[BUG] WeightRegression produces incorrect regression when thru_orig = False#1024
Bug
Assignees
henrydingliu
Labels
Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!
Description
@henrydingliu
henrydingliu
opened on Jun 19, 2026
Are you on the latest chainladder version?
  •  Yes, this bug occurs on the latest version.
Describe the bug in words
came across a bug in _fit_OLS while trying to recreate chapter 11. likely culprit is a missing w (or two) around here. should be a quick PR for the students in our contributor group
How can the bug be reproduced?
test=cl.Triangle(
data= {
'value':[100,200,300,400,500,0,0,0],
'weight':[1,1,1,1,1,0,0,0],
'ay': [2001,2002,2003,2004,2005,2006,2007,2008],
'dev':[2008,2008,2008,2008,2008,2008,2008,2008],
},
origin='ay',
development='dev',
columns=['value','weight'],
cumulative=True,
)
reg=cl.WeightedRegression(
axis=2,
thru_orig=False,
xp=test.get_array_module()
).fit(
np.ones((1,1,8,1)) *test.origin.year.values[None,None,:,None],
test['value'].values,
test['weight'].values
)
reg.slope_
What is the expected behavior?
100
Would you be willing to contribute this ticket?
  •  Yes, absolutely!
  •  Yes, but I would like some help.
  •  No.
Metadata
Metadata
Assignees
Labels
Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!
Type
Bug
Fields
Priority
Urgent
Effort
Low
Scope
Codebase
Projects
Milestone
No milestone
Relationships
None yet
Development
No branches or pull requests
Issue actions

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
[BUG] WeightRegression produces incorrect regression when thru_orig = False #1024
Open
Bug
Open
[BUG] WeightRegression produces incorrect regression when thru_orig = False#1024
Bug
Assignees
henrydingliu
Labels
Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!
Description
@henrydingliu
henrydingliu
opened on Jun 19, 2026
Are you on the latest chainladder version?
  •  Yes, this bug occurs on the latest version.
Describe the bug in words
came across a bug in _fit_OLS while trying to recreate chapter 11. likely culprit is a missing w (or two) around here. should be a quick PR for the students in our contributor group
How can the bug be reproduced?
test=cl.Triangle(
data= {
'value':[100,200,300,400,500,0,0,0],
'weight':[1,1,1,1,1,0,0,0],
'ay': [2001,2002,2003,2004,2005,2006,2007,2008],
'dev':[2008,2008,2008,2008,2008,2008,2008,2008],
},
origin='ay',
development='dev',
columns=['value','weight'],
cumulative=True,
)
reg=cl.WeightedRegression(
axis=2,
thru_orig=False,
xp=test.get_array_module()
).fit(
np.ones((1,1,8,1)) *test.origin.year.values[None,None,:,None],
test['value'].values,
test['weight'].values
)
reg.slope_
What is the expected behavior?
100
Would you be willing to contribute this ticket?
  •  Yes, absolutely!
  •  Yes, but I would like some help.
  •  No.
Metadata
Metadata
Assignees
Labels
Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!
Type
Bug
Fields
Priority
Urgent
Effort
Low
Scope
Codebase
Projects
Milestone
No milestone
Relationships
None yet
Development
No branches or pull requests
Issue actions

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
[BUG] WeightRegression produces incorrect regression when thru_orig = False #1024
Open
Bug
Open
[BUG] WeightRegression produces incorrect regression when thru_orig = False#1024
Bug
Assignees
henrydingliu
Labels
Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!
Description
@henrydingliu
henrydingliu
opened on Jun 19, 2026
Are you on the latest chainladder version?
  •  Yes, this bug occurs on the latest version.
Describe the bug in words
came across a bug in _fit_OLS while trying to recreate chapter 11. likely culprit is a missing w (or two) around here. should be a quick PR for the students in our contributor group
How can the bug be reproduced?
test=cl.Triangle(
data= {
'value':[100,200,300,400,500,0,0,0],
'weight':[1,1,1,1,1,0,0,0],
'ay': [2001,2002,2003,2004,2005,2006,2007,2008],
'dev':[2008,2008,2008,2008,2008,2008,2008,2008],
},
origin='ay',
development='dev',
columns=['value','weight'],
cumulative=True,
)
reg=cl.WeightedRegression(
axis=2,
thru_orig=False,
xp=test.get_array_module()
).fit(
np.ones((1,1,8,1)) *test.origin.year.values[None,None,:,None],
test['value'].values,
test['weight'].values
)
reg.slope_
What is the expected behavior?
100
Would you be willing to contribute this ticket?
  •  Yes, absolutely!
  •  Yes, but I would like some help.
  •  No.
Metadata
Metadata
Assignees
Labels
Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!
Type
Bug
Fields
Priority
Urgent
Effort
Low
Scope
Codebase
Projects
Milestone
No milestone
Relationships
None yet
Development
No branches or pull requests
Issue actions

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
[BUG] WeightRegression produces incorrect regression when thru_orig = False #1024
Open
Bug
Open
[BUG] WeightRegression produces incorrect regression when thru_orig = False#1024
Bug
Assignees
henrydingliu
Labels
Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!
Description
@henrydingliu
henrydingliu
opened on Jun 19, 2026
Are you on the latest chainladder version?
  •  Yes, this bug occurs on the latest version.
Describe the bug in words
came across a bug in _fit_OLS while trying to recreate chapter 11. likely culprit is a missing w (or two) around here. should be a quick PR for the students in our contributor group
How can the bug be reproduced?
test=cl.Triangle(
data= {
'value':[100,200,300,400,500,0,0,0],
'weight':[1,1,1,1,1,0,0,0],
'ay': [2001,2002,2003,2004,2005,2006,2007,2008],
'dev':[2008,2008,2008,2008,2008,2008,2008,2008],
},
origin='ay',
development='dev',
columns=['value','weight'],
cumulative=True,
)
reg=cl.WeightedRegression(
axis=2,
thru_orig=False,
xp=test.get_array_module()
).fit(
np.ones((1,1,8,1)) *test.origin.year.values[None,None,:,None],
test['value'].values,
test['weight'].values
)
reg.slope_
What is the expected behavior?
100
Would you be willing to contribute this ticket?
  •  Yes, absolutely!
  •  Yes, but I would like some help.
  •  No.
Metadata
Metadata
Assignees
Labels
Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!
Type
Bug
Fields
Priority
Urgent
Effort
Low
Scope
Codebase
Projects
Milestone
No milestone
Relationships
None yet
Development
No branches or pull requests
Issue actions

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
[BUG] WeightRegression produces incorrect regression when thru_orig = False #1024
Open
Bug
Open
[BUG] WeightRegression produces incorrect regression when thru_orig = False#1024
Bug
Assignees
henrydingliu
Labels
Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!
Description
@henrydingliu
henrydingliu
opened on Jun 19, 2026
Are you on the latest chainladder version?
  •  Yes, this bug occurs on the latest version.
Describe the bug in words
came across a bug in _fit_OLS while trying to recreate chapter 11. likely culprit is a missing w (or two) around here. should be a quick PR for the students in our contributor group
How can the bug be reproduced?
test=cl.Triangle(
data= {
'value':[100,200,300,400,500,0,0,0],
'weight':[1,1,1,1,1,0,0,0],
'ay': [2001,2002,2003,2004,2005,2006,2007,2008],
'dev':[2008,2008,2008,2008,2008,2008,2008,2008],
},
origin='ay',
development='dev',
columns=['value','weight'],
cumulative=True,
)
reg=cl.WeightedRegression(
axis=2,
thru_orig=False,
xp=test.get_array_module()
).fit(
np.ones((1,1,8,1)) *test.origin.year.values[None,None,:,None],
test['value'].values,
test['weight'].values
)
reg.slope_
What is the expected behavior?
100
Would you be willing to contribute this ticket?
  •  Yes, absolutely!
  •  Yes, but I would like some help.
  •  No.
Metadata
Metadata
Assignees
Labels
Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!
Type
Bug
Fields
Priority
Urgent
Effort
Low
Scope
Codebase
Projects
Milestone
No milestone
Relationships
None yet
Development
No branches or pull requests
Issue actions

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
[BUG] WeightRegression produces incorrect regression when thru_orig = False #1024
Open
Bug
Open
[BUG] WeightRegression produces incorrect regression when thru_orig = False#1024
Bug
Assignees
henrydingliu
Labels
Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!
Description
@henrydingliu
henrydingliu
opened on Jun 19, 2026
Are you on the latest chainladder version?
  •  Yes, this bug occurs on the latest version.
Describe the bug in words
came across a bug in _fit_OLS while trying to recreate chapter 11. likely culprit is a missing w (or two) around here. should be a quick PR for the students in our contributor group
How can the bug be reproduced?
test=cl.Triangle(
data= {
'value':[100,200,300,400,500,0,0,0],
'weight':[1,1,1,1,1,0,0,0],
'ay': [2001,2002,2003,2004,2005,2006,2007,2008],
'dev':[2008,2008,2008,2008,2008,2008,2008,2008],
},
origin='ay',
development='dev',
columns=['value','weight'],
cumulative=True,
)
reg=cl.WeightedRegression(
axis=2,
thru_orig=False,
xp=test.get_array_module()
).fit(
np.ones((1,1,8,1)) *test.origin.year.values[None,None,:,None],
test['value'].values,
test['weight'].values
)
reg.slope_
What is the expected behavior?
100
Would you be willing to contribute this ticket?
  •  Yes, absolutely!
  •  Yes, but I would like some help.
  •  No.
Metadata
Metadata
Assignees
Labels
Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!
Type
Bug
Fields
Priority
Urgent
Effort
Low
Scope
Codebase
Projects
Milestone
No milestone
Relationships
None yet
Development
No branches or pull requests
Issue actions

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

Skip to content
[BUG] WeightRegression produces incorrect regression when thru_orig = False #1024
Open
Bug
Open
[BUG] WeightRegression produces incorrect regression when thru_orig = False#1024
Bug
Assignees
henrydingliu
Labels
Great First Contribution! 🌱Beginner friendly tickets with narrow scope and huge impact. Perfect to get your feet wet!
Description
@henrydingliu
henrydingliu
opened on Jun 19, 2026
Are you on the latest chainladder version?
  •  Yes, this bug occurs on the latest version.
Describe the bug in words
came across a bug in _fit_OLS while trying to recreate chapter 11. likely culprit is a missing w (or two) around here. should be a quick PR for the students in our contributor group
How can the bug be reproduced?
test=cl.Triangle(
data= {
'value':[100,200,300,400,500,0,0,0],
'weight':[1,1,1,1,1,0,0,0],
'ay': [2001,2002,2003,2004,2005,2006,2007,2008],
'dev':[2008,2008,2008,2008,2008,2008,2008,2008],
},
origin='ay',
development='dev',
columns=['value','weight'],
cumulative=True,
)
reg=cl.WeightedRegression(
axis=2,
thru_orig=False,
xp=test.get_array_module()
).fit(
np.ones((1,1,8,1)) *test.origin.year.values[None,None,:,None],
test['value'].values,
test['weight'].values
)
reg.slope_
What is the expected behavior?
100
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