Double becomes int32 --why??

My goal is to write a file that has a column of double precision numbers for each subject. Here's what I have:

    TadvDiff(1,qq) = currsubj; %Heading that displays subject ID number
    TadvDiff(2:(timepoints+1),qq) = TminusC;

currsubj and TminusC are both double-precision. Somehow, TadvDiff is int32.

After looping through each subject, I write TadvDiff to a file:

    dlmwrite('TadvDiffN108.txt',TadvDiff,'delimiter','\t','precision', '%.4f');

which ends up being all 1s and 0s when I need decimals. Why did my doubles become ints, and how can I correct this?

Thanks!

[ANJ]

I should maybe add that 1) I've read about precision problems with dlmwrite, but the value of TadvDiff is already an int32 before I call that function; and 2) I'm using the student version of Matlab, 7.10 if that is useful info.

Thanks again!

[Walter Roberson]

How did you initialize TadvDiff ?

[ANJ]

The code that I've shown is the first time I've defined TadvDiff.

[Walter Roberson]

Somehow, the very first time you write into TadvDiff, you must be storing int32. That very first write determines the datatype after that.

Can you reasonably pre-allocate your TadvDiff array? e.g.,

TadvDiff = zeros(timepoints+1, 17);

[ANJ]

Great, that did the trick! Thanks so much!