Conversion to double from struct is not possible.

Hello,

When I try to run the following code, it gives me an error at topo_GA with "The following error occurred converting from struct to double:

Error using double
Conversion to double from struct is not possible."

inDir = 'F:\SSVEP study\Data\attnSSVEP\SSVEP_Data\Topography Analysis\Attn Left No Task attn7.14Hz v 11.1Hz\14Hz\';
files = dir([inDir '*.mat']);
outDir = 'F:\SSVEP study\Data\attnSSVEP\SSVEP_Data\Topography Analysis\Attn Left No Task attn7.14Hz v 11.1Hz\14Hz\Final_14Hz\';

topo_GA = [];

for s =  1:length(files)
    filename = files(s).name;
    x =  load([inDir filename]);
    topo_GA(s,:) = x;
end

     d = mean(topo_GA,1);
     figure;topoplot(d, 'biosemi_64.loc');

Can anyone help me to get rid of the error.

Thanks

Yatin

Answer 1

[Guillaume]

When you do

x = load([inDir filename]); %x is a poor variable name.

x is a structure with fields that are named after the variables in the file. You then assign the structure to topo_GA so topo_GA is also a structure (and as a potential bug, if any of the file you load contains a variable that is not in the other files, the assignment will fail).

You can't take the mean of a structure, hence the error you get. I assume that it's a particular variable in the mat file that you want the mean of, and you'll have to specify it, either when you assign x to topo_GA (best) or when you take the mean:

topo_GA(s, :) = x.somevarname; %less chance of breaking in the future

or

d = mean(topo_GA(s, :).somevarname, 1);

Obviously replace somevarname by the actual name of the variable.

[Yatin]

Thank you Guillaume. Adding the variable name did the trick. One of the files int he list had a different variable name which was creating the problem.

Many thanks Yatin