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Turn a structure into an array

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Sara
Sara on 1 Dec 2011
Hello everybody,
i'm starting with matlab and i have a problem with this code:
ev = load('EV.mat'); %potenciales evocados
fs = 3200; %sampling rate = 3200 Hz
slen = length(ev);
t=[1:slen]/fs;
vent=256; %amplitud ventana
sum=zeros(1,vent); %vector de ceros con 256 elementos
n=100; %numero de realizaciones
for i=0:vent-1
for k=1:25600
sum(i+1)=sum(i+1)+ev(i+k);
k=k+256;
end
end
i should sum 100 windows, each one containing 256 samples, of the same signal, the signal ev.Tthe problem is that the program gives me the following errors:
??? Undefined function or variable 'ev'.
??? Undefined function or method 'plus' for input arguments of type 'struct'.
Error in ==> Potenciales_Evocados at 17 sum(i+1)=sum(i+1)+ev(i+k);
Then, i guess i should transform this structure into an array, but i don't know how..! I've tried with "c = struct2cell(s)" but i create a cell array and the error is the same ??? Undefined function or method 'plus' for input arguments of type 'cell'.
In the command window i have this:
ev =
ev: [727040x1 double]
>> length(ev)
ans =
1
Please can anyone help me? Thank you very much in advance

Accepted Answer

Jan
Jan on 1 Dec 2011
It seems like after:
ev = load('EV.mat')
"ev" is a struct, which contains the field "ev". So try this:
Data = load('EV.mat')
ev = Data.ev;
BTW. using "sum" as name of a variable shadows the built-in function with the same name. It is recommend to avoid such shadowing, because it leads to unexpected results frequently.
A faster method to sum the chunks without loops:
S = sum(reshape(ev, 256, []), 2);

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