Is there a way to use a for loop to loop through structure fields?

Hello, I am creating an aerodynmic database in which I have my data organized within a structure. I am looking for a way to use a for loop to access data fields within a structure. The fields I am interested in acessing are 4D doubles which I would like to send to a function to plot.

Essentially I was wondering if there is anyway to do something like this:

mystruct.field1 = A % A, B, C are M x N x M x N arrays 
mystruct.field2 = B
mystruct.field3 = C

fieldvec = {'field1', 'field2', 'field3'}

for i = 1:length(fieldvec)
    plottingfunction(mystruct.fieldvec{i})
end

As oppsed to hard coding it like this:

plottingfunction(mystruct.fieldvec1)
plottingfunction(mystruct.fieldvec2)
plottingfunction(mystruct.fieldvec3)

Thanks!

Answer 1

[the cyclist]

Yes, you can. (Here, I just check the size, instead of calling a function.)

mystruct.field1 = rand(2,3,5,7);
mystruct.field2 = rand(3,5,7,11);
mystruct.field3 = rand(5,7,11,13);

fieldvec = {'field1', 'field2', 'field3'};

for i = 1:length(fieldvec)
    size(mystruct.(fieldvec{i})) % Note the parentheses I added
end

ans = 1×4

2 3 5 7

ans = 1×4

3 5 7 11

ans = 1×4

5 7 11 13

Here is a more compact (and I think intuitive) approach

rng default

mystruct.field1 = rand(2,3,5,7); % A, B, C are M x N x M x N arrays 
mystruct.field2 = rand(3,5,7,11);
mystruct.field3 = rand(5,7,11,13);

fieldvec = ["field1", "field2", "field3"];

for f = fieldvec
    size(mystruct.(f))
end

ans = 1×4

2 3 5 7

ans = 1×4

3 5 7 11

ans = 1×4

5 7 11 13

[Milo Bouchard]

Thanks alot!

Answer 2

[Voss]

mystruct.field1 = A % A, B, C are M x N x M x N arrays 
mystruct.field2 = B
mystruct.field3 = C

fieldvec = fieldnames(mystruct);

for i = 1:numel(fieldvec)
    plottingfunction(mystruct.(fieldvec{i}))
end

[Voss]

https://www.mathworks.com/help/matlab/matlab_prog/generate-field-names-from-variables.html

Answer 3

[Walter Roberson]

A = 'A data here'; B = 'B data here'; C = 'C data here';

mystruct.field1 = A % A, B, C are M x N x M x N arrays 

mystruct = struct with fields:
    field1: 'A data here'

mystruct.field2 = B

mystruct = struct with fields:
    field1: 'A data here'
    field2: 'B data here'

mystruct.field3 = C

mystruct = struct with fields:
    field1: 'A data here'
    field2: 'B data here'
    field3: 'C data here'

fieldvec = {'field1', 'field2', 'field3'}

fieldvec = 1×3 cell array
    {'field1'}    {'field2'}    {'field3'}

for i = 1:length(fieldvec)
    plottingfunction(mystruct.(fieldvec{i}));
end

data = 'A data here'

data = 'B data here'

data = 'C data here'

function plottingfunction(data)
   data
end