Problems in using "dwtest"

I have a simple Tx3 matrix of residuals. I want to apply to it the dwtest to test for autocorrellation (I also used autocorr but still I'd like to see a statistic).

However, when I try to implement it, I get:

dwtest(VAR1.res(:, 1), 'Exact')
Error using qr
Invalid data type. First argument must be double or single.

Error in pvaluedw (line 34)
    [Q,~] = qr(X);

Error in dwtest (line 100)
pdw = pvaluedw(dw,X,option);
 
% but it it is indeed "double"

 class(VAR1.res(:,1))

ans =

    'double'

What am I doing wrong?

Answer 1

[Tommy]

The error is saying the first argument to qr() must be double or single. That first argument is X, and if you comb through dwtest and pvaluedw you'll see that X is actually your second argument to dwtest, in this case 'Exact' - not a double.

You'll have to match the syntax of dwtest from https://www.mathworks.com/help/stats/dwtest.html :

p = dwtest(r,x,'Method','exact')

[Armando MAROZZI]

thank you Tommy! silly mistake!