How to create an indexable array of fid

To open a file:

fid = fopen('speedygo_nCores.bat','wt');

and given:

nCores=6;

What is the syntax to declare a fid array of size nCores? So as to be able to implement:

for i=1:nCores
    goFilename = strcat('speedygo_' , i, '.bat' ); 
    fid(i)=fopen(goFilename,'wt');
end

The goal is to enumerate the fid(i), where i = {1,2,3...nCores} and for use in fprintf:

fprintf(fid(i),"hello world");

Can a cell hold the six fids? or is there a better technique?

Answer 1

[Matt J]

fids are just numbers. You can allocate any double array to hold them.

[Raymond Chiu]

Thanks for responding. Given:

nCores = 6;
for i=1:nCores
    goFilename = strcat('speedygo_' , i, '.bat' ); 
    fid(i)=fopen(goFilename,'wt');
end

Do I need to somehow need to declare fid as double? I think the snippet above will meet the objetive or is there anything else I missed? Again thanks

[Walter Roberson]

nCores = 6;
fid = zeros(nCores,1);
for i=1:nCores
    goFilename = "speedygo_" + i + ".bat"; 
    fid(i) = fopen(goFilename,'wt');
end

pre-allocation is just a matter of efficiency here.

However when you pass in i to strcat like that, the result would be the same as if you had done

    goFilename = ['speedygo_' , char(i), '.bat' ];

as in the first one being speedygo_ followed by Start of Heading character https://www.compart.com/en/unicode/U+0001

Using an integer in strcat() or [] with character vectors converts the integer to its exact character code, and does not convert the integer to the ascii representation of the digits. char(1) is not the same as '1' which is char(49)

[Stephen23]

"pre-allocation is just a matter of efficiency here."

Preallocation also significantly increases robustness.