Matlab built-in function not identified

I am trying to use the function coefTest from the Statistics and Machine Learning Toolbox after calling the function I recive the error message

Undefined function or variable 'coefTest'.

I have checked that the statistics and machine learning toolbox is installed and enabled, has anybody else has an idea on how to further truble shoot this issue?

Thanks

Answer 1

[Bora Eryilmaz]

coefTest is not a "function". It is a "method" of the LinearModel object/class. So, in order to call it, you need to create a linear model first. Something like this:

m = fitlm(array2table(rand(10,2)))

m = 
Linear regression model:
    Var2 ~ 1 + Var1

Estimated Coefficients:
                   Estimate      SE        tStat       pValue 
                   ________    _______    ________    ________

    (Intercept)    0.80105     0.27121      2.9536    0.018324
    Var1           -0.4655     0.48461    -0.96057      0.3649


Number of observations: 10, Error degrees of freedom: 8
Root Mean Squared Error: 0.327
R-squared: 0.103,  Adjusted R-Squared: -0.00866
F-statistic vs. constant model: 0.923, p-value = 0.365

coefTest(m)

ans = 0.3649

[Fangjun Jiang]

Fresh start from MATLAB, "help coefTest" shows nothing but "doc coefTest" gives doc

Once fitlm() is executed, "help coefTest" shows the help text

[Bora Eryilmaz]

Seems to be working for me and here. It probably has something to do with the creation of a LinearModel that brings the help for the coefTest() method into scope:

help coefTest

--- help for classreg.regr.CompactGeneralizedLinearModel/coefTest ---

 coefTest Linear hypothesis test on coefficients.
    P = coefTest(M) computes the p-value for an F test that all
    coefficient estimates in the regression model M except the intercept
    are zero.
 
    P = coefTest(M,H), with H a numeric matrix having one column for each
    coefficient, performs an F test that H*B=0, where B represents the
    coefficient vector.
 
    P = coefTest(M,H,C) accepts a vector C having one value for each row
    of H, and it performs an F test that H*B=C.
 
    [P,F,R] = coefTest(...) also returns the F-statistic F and the rank R
    of the matrix H. The F statistic has R degrees of freedom in the
    numerator and M.DFE degrees of freedom in the denominator.
 
    Example:
        % Test the significance of the Weight^2 coefficient, and note that
        % the p-value is the same as in the coefficients display.
        load carsmall
        d = dataset(MPG,Weight);
        d.Year = ordinal(Model_Year);
        lm = fitlm(d,'MPG ~ Year + Weight + Weight^2')
        p = coefTest(lm,[0 0 0 0 1])
 
        % Test the significance of both coefficients for the categorical
        % predictor Year, and note that the p-value is the same as in the
        % anova table display.
        anova(lm)
        p = coefTest(lm,[0 0 1 0 0;0 0 0 1 0])
 
    See also LinearModel, GeneralizedLinearModel, NonLinearModel, linhyptest.

Help for classreg.regr.CompactGeneralizedLinearModel/coefTest is inherited from superclass classreg.regr.CompactTermsRegression

    Documentation for classreg.regr.CompactGeneralizedLinearModel/coefTest
       doc classreg.regr.CompactGeneralizedLinearModel/coefTest

    Other uses of coefTest

       classreg.regr.CompactParametricRegression/coefTest
       RepeatedMeasuresModel/coefTest

[Steven Lord]

Fresh start from MATLAB, "help coefTest" shows nothing but "doc coefTest" gives doc

That's correct. Not all classes in MATLAB are loaded into memory on MATLAB startup, IIRC. If the classes aren't loaded MATLAB won't know about the methods. Constructing an instance of a class makes MATLAB load the class definition into memory and I believe help looks at what's in memory. The doc function doesn't care what's in memory.

Answer 2

[Steven Lord]

According to a search there are several different functions named coefTest in Statistics and Machine Learning Toolbox. From a quick scan of their documentation pages I believe the reason you're unable to call the function is that each of them requires that their first input is a certain type of object. If you were to try to call them with something other than one of those specific types of objects as the first input, MATLAB would not know to call that function.

coefTest(1:10) % won't work

Unrecognized function or variable 'coefTest'.