MATLAB: Iterations on field conditions of a structure array

Question

Hi. I am working with a structure array S (1 X 50,000) with 10 fields. I want to find few paramters based on few conditions. Is there a simple way to do such iterations shown below using a loop and save them in a structure?

f1 = [S.f1];
f2 = [S.f2];
f3 = [S.f3];
%% ITERATION 1:
idx1 = f1 > 0 & f1 <=10;
% Parameter 1

num1 = numel(f1(idx1));
avg1 = mean(f2(idx));
sd1 = std(f2(idx));
% Parameter 2

idx2 = f3 > 0;
idx = idx1 & idx2;
pos_num1 = numel(f1(idx));
pos_avg1 = mean(f2(idx));
pos_sd1 = std(f2(idx));
% Parameter 3

idx2 = f3 < 0;
idx = idx1 & idx2;
neg_num1 = numel(f1(idx));
neg_avg1 = mean(f2(idx));
neg_sd1 = std(f2(idx));
%% ITERATION 2:
idx1 = f1 > 10 & f1 <=20;
% Parameter 1
num2 = numel(f1(idx1));
avg2 = mean(f2(idx));
sd2 = std(f2(idx));
% Parameter 2
idx2 = f3 > 0;
idx = idx1 & idx2;
pos_num2 = numel(f1(idx));
pos_avg2 = mean(f2(idx));
pos_sd2 = std(f2(idx));
% Parameter 3
idx2 = f3 < 0;
idx = idx1 & idx2;
neg_num2 = numel(f1(idx));
neg_avg2 = mean(f2(idx));
neg_sd2 = std(f2(idx));
% so on till 20 interations.

The result should be saved like:

Result.num=[num1,num2,num3………,num20];

Result.pos_num=[pos_num1,pos_num2,pos_num3,…..,pos_num20];

Result.neg_num=[neg_num1,neg_num2,neg_num2,……,neg_num20];

Result.avg=[avg1,avg2,avg3,…..avg20];

.. so on.

Any help will be highly appreciated.

Answer 1

Hi,

It is not very clear from your explanation what you are trying to accomplish. If you are trying to iterate using indices that satisfy some conditions, you should make a matrix with each column containing indices of vector 'f1' that satisfy the required conditions. For example,

idx_list = [(f1 > 0 & f1 <= 10) (f1 > 10 & f1 <= 20) (f1 > 20 & f1 <= 30)];
idx_list_size = 3;
num_list = zeros(idx_list_size, 1);

And iterate in the following way:

for i=1:idx_list_size
    num_list(i) = numel(f1(idx_list(:, i)));
end