fopen problem using updated software

I use fopen(fid,"w") in matlab 2015b in windows, the function works well. But as I switch to matlab 2017a in mac, student use.

I have the following error:

First Input must be a file name or a file identifier.

I am wondering what's wrong?

Thanks.

b

[Walter Roberson]

Please show more of your code including how you construct the variable "fid"

Note: it is quite common that the variable fid is used for a numeric file identifier returned from fopen(), rather than for the file name.

Question: are you reading the file name from a file using importdata() ?

[Stephen23]

@Kan Yao: please explain to us what fid is, or how it is created.

Answer 1

[Jan]

As the documentation and the error message explains, the standard calling is:

fid = fopen(FileName, 'w')

Here fid is a numerical file identifier and FileName is the string containing the name of the file.