How to save struct data in for loop
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Suman Chatterjee
on 23 Oct 2020
Answered: Nitin Kapgate
on 28 Oct 2020
Hi,
I am working in a for loop where for each iteration I get a new structure data with 3 fields in all of them. How do I store all of these data points so that I could use them together? I tried working with the following format but I am getting the error "Subscripted assignment between dissimilar structures."
The m.get_data() returns a struct of three fields each containg 1024 values.
for i=1:10
data_struct(i)=m.get_data();
end
5 Comments
Walter Roberson
on 23 Oct 2020
Use dynamic structure names so your data_struct is a struct with multiple field names. Then use save() with the -struct option; that will create one variable name in the .mat file for each field name in the struct.
Accepted Answer
Nitin Kapgate
on 28 Oct 2020
You can overcome the problem by pre-allocating the array of structures as follows:
clear all; % Clear the workspace
N = 10;
% Pre-allocate the array of structures
structArray1(N) = struct('field1',[], 'field2',[], 'field3',[]);
for i=1:N
field1 = "field1";
field2 = "field2";
field3 = "field3";
structArray1(i)=getStruct(field1, field2,field3);
end
Alternatively, instead of pre-allocating before the loop, you can also loop backwards so that all the memory allocation is done in the first iteration itself.
N = 10;
for i=N:-1:1
field1 = "field1";
field2 = "field2";
field3 = "field3";
structArray2(i)=getStruct(field1, field2,field3);
end
structArray2 = fliplr(structArray2); % Get back the array of structures in correct order
The getStruct function is as follows:
function outStruct = getStruct(field1, field2,field3)
% returns a struct with 3 fields
outStruct.field1 = field1;
outStruct.field2 = field2;
outStruct.field3 = field3;
end
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