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Fix empty array edge cases in stepwisefit #484

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Merged
pr0m1th3as merged 4 commits into from
Sep 15, 2026
+44 −11
Merged

Fix empty array edge cases in stepwisefit #484

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323ee1a
Fix empty array edge cases in stepwisefit
Sonu0305 Sep 14, 2026
6821bcb
Refactor tests to use %!error instead of %!fail
Sonu0305 Sep 14, 2026
8e0f953
Fix stepwisefit empty array logic and tests
Sonu0305 Sep 14, 2026
737ecd8
Apply 80-char limits to stepwisefit.m
Sonu0305 Sep 14, 2026
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55 changes: 44 additions & 11 deletions inst/Regression/stepwisefit.m
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Original file line number Diff line number Diff line change
Expand Up @@ -139,15 +139,21 @@
error ("stepwisefit: at least two input arguments required");
endif

if (! ismatrix (X) || ! isvector (y))
error ("stepwisefit: X must be a matrix and y a vector");
if (! ismatrix (X))
error ("stepwisefit: X must be a matrix.");
endif
if (! (isvector (y) || isempty (y)))
error ("stepwisefit: Y must be a column vector.");
endif
if (! iscolumn (y))
error ("stepwisefit: Y must be a column vector.");
endif

y = y(:);

## Validate row compatibility BEFORE any concatenation
if (rows (X) != rows (y))
error ("stepwisefit: X must be a matrix and y a vector");
error ("stepwisefit: X and Y must have the same number of rows.");
endif

## Parse Name-Value pairs
Expand Down Expand Up @@ -189,7 +195,8 @@

## Validate PRemove (if provided)
if (! isempty (PRemove))
if (! (isscalar (PRemove) && isnumeric (PRemove) && PRemove > 0 && PRemove < 1))
if (! (isscalar (PRemove) && isnumeric (PRemove) && PRemove > 0
&& PRemove < 1))
error ("stepwisefit: PRemove must be a scalar strictly between 0 and 1");
endif
if (PRemove < PEnter)
Expand All @@ -198,7 +205,8 @@
endif

## Validate MaxIter
if (! (isscalar (MaxIter) && isnumeric (MaxIter) && MaxIter > 0 && fix (MaxIter) == MaxIter))
if (! (isscalar (MaxIter) && isnumeric (MaxIter) && MaxIter > 0
&& fix (MaxIter) == MaxIter))
error ("stepwisefit: MaxIter must be a positive integer");
endif

Expand All @@ -210,6 +218,24 @@
n = rows (Xc);
p = columns (Xc);

if (n == 0)
b = NaN (p, 1);
se = NaN (p, 1);
pval = NaN (p, 1);
finalmodel = false (1, p);
stats = struct ('source', 'stepwisefit', 'df0', -1, 'dfe', 0, ...
'SStotal', 0, 'SSresid', 0, 'fstat', NaN, 'pval', NaN, ...
'rmse', NaN, 'intercept', 0, 'wasnan', wasnan, ...
'xr', zeros(0, p), 'yr', zeros(0, 1), 'B', NaN (p, 1), ...
'SE', NaN (p, 1), 'TSTAT', NaN (p, 1), ...
'PVAL', NaN (p, 1), ...
'covb', NaN (p, p));
history = struct ('B', zeros (p, 0), 'rmse', zeros (0, 0), ...
'df0', zeros (0, 0), 'in', false (0, p));
nextstep = 0;
return;
endif

## Validate Keep and InModel type (if provided)
if (! isempty (Keep) && ! islogical (Keep))
error ("stepwisefit: Keep must be a logical vector");
Expand Down Expand Up @@ -649,22 +675,29 @@
%! [b1] = stepwisefit (X, y);
%! [b2] = stepwisefit (X, y, 'Scale', 'on');
%! assert_equal (rows (b1) == rows (b2), true);
%!test
%! X = randn (20,4);
%! y = randn (20,1);
%! fail ('stepwisefit (X,y,''Keep'',[true false])');
%!error <stepwisefit: Keep length must match number of predictors> ...
%! stepwisefit (randn (20,4), randn (20,1), 'Keep', [true false])

## Test input validation
%!error <stepwisefit: at least two input arguments required> ...
%! stepwisefit ()
%!error <stepwisefit: X must be a matrix and y a vector> ...
%!error <stepwisefit: X must be a matrix.> ...
%! stepwisefit (ones (2,2,2), [1;2])
%!error <stepwisefit: X must be a matrix and y a vector> ...
%!error <stepwisefit: X and Y must have the same number of rows.> ...
%! stepwisefit (ones (3,2), ones (2,1))
%!error <stepwisefit: unrecognized input arguments> ...
%! stepwisefit (randn (10,2), randn (10,1), 'UnknownOpt', 5)
%!error <stepwisefit: Display must be 'on' or 'off'> ...
%! stepwisefit (randn (10,2), randn (10,1), 'Display', 'maybe')

%!test
%! ## Edge cases with empty arrays
%! b = stepwisefit (zeros (0, 3), zeros (0, 1), 'Display', 'off');
%! assert_equal (size (b), [3 1]);
%! assert_equal (isnan (b), true (3, 1));
%!
%!error <stepwisefit: Y must be a column vector.> ...
%! stepwisefit ([], [], 'Display', 'off')
%!error <stepwisefit: Scale must be 'on' or 'off'> ...
%! stepwisefit (randn (10,2), randn (10,1), 'Scale', 123)
%!error <stepwisefit: PEnter must be a scalar strictly between 0 and 1> ...
Expand Down