assign value for field in a struct using a loop

Hi

am trying to save variables into structure using a loop but i have a problem assigning fieldnames and values so what i did was

b = 1:50;

field = ['Contrast_' num2str(b) ] yet i dont know how to assign the value of Contrast to this field.

i tried something like value = (field) or value = [field] but it doesn't retrieve the value of the variable.

what am doing is measuring contrast for each slice for an image in a loop so it is important for me to relate the slice number to the contrast value but i also want to save all of the contrast values in struct in the end where the field name is the contrast_'sliceNumber'.

any help is appreciated.

thanks Hannah

[Jan]

You write of "structures" - do you mean "structs"? Your code does not contain structs or fields.

[Hannah]

yes i mean struct. and i didnt put the complete code because it is very long and i needed help with using field names and values in a loop.

Hannah

Answer 1

[Jan]

As Image Analyst has written already, hiding an index in teh field name is a bad idea:

for k = 1:10
  S.(sprintf('Contrast_%d', k)) = rand;
end

It is much better to use an array:

S.Contrast = zeros(1, 10);
for k = 1:10
  S.Contrast(k) = rand;
end

[Hannah]

Thank you.

Answer 2

[Image Analyst]

This is not advised. Read the FAQ: http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F You should use one field that is an array, not tons of fields with different names.

[Hannah]

Thank you for your help. the issue is that am measuring many parameters for each image i have for multiple data sets and i started by creating a cell array but it became difficult to find what i needed easily so i tried saving all the parameters i measured in each slice in one struct under different field names.

[Image Analyst]

That should not be the case. In fact it should be the opposite. What you want to do is more complicated, as you know because you have to ask us. Jan gave you the code. It's not difficult at all - how much simpler can it be?