regression_ftest
statistics: h = regression_ftest (y, x)
statistics: h = regression_ftest (y, x, keep)
statistics: h = regression_ftest (…, Name, Value)
statistics: [h, p, stats] = regression_ftest (…)
F-test for nested linear regression models.
Fit the full linear model of the response y on every column of
x, and a reduced model on the columns of x indexed by
keep, both by least squares, and test the null hypothesis that the
columns the reduced model leaves out add nothing to it. keep holds
column indices or a logical mask; left out or empty, the reduced model has
no predictors and the test is of every column of x together. Both
models include a constant term unless 'Intercept' is false.
y must be a vector with one element per row of x, and neither
may contain missing values.
The test decision is returned in h, which is 1 when the null hypothesis is rejected at the significance level alpha and 0 otherwise, and the p-value in p. stats is a structure with the following fields:
fstat | the F statistic. |
df1 | its numerator degrees of freedom, the number of coefficients the reduced model leaves out. |
df2 | its denominator degrees of freedom, the residual degrees of freedom of the full model. |
betafull | the coefficients of the full model, the constant first where there is one. |
betareduced | those of the reduced model. |
ssefull | the residual sum of squares of the full model. |
ssereduced | that of the reduced model. |
CohensF2 | Cohen’s f^2, the effect size of the columns tested. |
CohensF2CI | its 100 (1 - alpha)% confidence interval. |
The degrees of freedom come from the ranks of the two designs. Cohen’s
f^2 is taken, as Cohen defines it, from the noncentrality of the F
statistic, lambda = f^2 (df1 + df2 + 1): the point estimate from
max (F df1 (df2 - 2) / df2 - df1, 0), unbiased for the noncentrality
before its truncation at zero, and the interval by inverting the noncentral
F distribution. Where the interval would need a noncentrality above
10^5, where ncfcdf loses accuracy, it is NaN.
The following Name/Value pairs are accepted:
'Alpha' | the significance level of h and the level of the confidence interval. Default is 0.05. |
'Intercept' | whether both models include a constant term. Default is true. |
The same tests, and any linear hypothesis on the coefficients, are available
from a fitted LinearModel through its coefTest method.
See also: regression_ttest, regress, fitlm
Source Code: regression_ftest