# How to use indexing to identify data in data(1, :) from points identifed in data(2,:)?

1 view (last 30 days)
Tomaszzz on 21 May 2022
Commented: Walter Roberson on 22 May 2022
Hi all,
I have a 2x17205 array (called vas_med_env; attached).
in vas_med_env(2,:) I have identified :
j= [5.8150 6.8350 7.8550 8.850]
Now I want to use j, to ''extract' data in vas_med_env(1,:) , by using indexing
my approach below:
n = length(j)-1;
vas_med_cycle = cell(n,1) ;
for i = 1:n
vas_med_cycle{i} = (vas_med_env(1, :),(vas_med_env(2, :),j(i):j(i+1))) ;
end
results in
vas_med_cycle{i} = (vas_med_env(1, :),(vas_med_env(2, :),j(i):j(i+1))) ;
Error: Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check
for mismatched delimiters.

Walter Roberson on 21 May 2022
You have a right-hand side expression of the form
(A, (B, C))
That has no meaning in MATLAB.
MATLAB does not define any way to create "tuples". That expression would not create a tuple in which the first element is A and the second element is a tuple in which the first element is B and the second element is C.
Perhaps you meant
vas_med_cycle{i} = {vas_med_env(1, :), {vas_med_env(2, :),j(i):j(i+1)}} ;
or perhaps you meant
vas_med_cycle{i} = [vas_med_env(1, :), vas_med_env(2, :), j(i):j(i+1)] ;
Walter Roberson on 22 May 2022
I wonder if you want something closer to
idx1 = j(1):j(2)-1;
idx2 = j(2):j(3)-1;
idx3 = j(3):j(4);

### Categories

Find more on Matrix Indexing in Help Center and File Exchange

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by