How to loop two vectors in MATLAB?

问题

In python one can use zip to loop multiple vectors or enumerate to get the current index of the looped vector like so

one = ['A', 'B', 'C']
two = [1, 2, 3]

for i, j in zip(one, two):
    print i, j

for j, i in enumerate(one):
    print i, two[j]

Gives

>>> 
A 1
B 2
C 3
A 1
B 2
C 3

In MATLAB it's possible to do

one = {'A' 'B' 'C'};
two = [1 2 3];

for i = 1:1:length(one)
  printf('%s %i\n', one{i}, two(i));
endfor

j = 1;
for i = one
  printf('%s %i\n', i{1}, two(j));
  j = j + 1;
endfor

giving

A 1
B 2
C 3
A 1
B 2
C 3

So is one of those two options the common way how one would do it in MATLAB, i. e. to loop through several vectors "in parallel" or is there another, maybe better way?

Bonus:

two = [1 2 3];
two = [1, 2, 3];

Both of these lines give the same output in the upper MATLAB program. Whats the difference?

回答1:

Using printf, or fprintf in Matlab, is pretty good. The Matlab code for your first approach is

one = {'A' 'B' 'C'};
two = [1 2 3];

for ii = 1:length(one)
  fprintf('%s %i\n', one{ii}, two(ii));
end

It's also possible to put the strings into a cell array, without any for loop.

s = cellfun(@(a,b) [a,' ',b], one', ...
    arrayfun(@num2str, two', 'UniformOutput', false),....
    'UniformOutput', false)

Bonus:

>> A = [1;2;3]   
A =
     1
     2
     3
>> A = [1 2 3]   
A =
     1     2     3
>> A = [1,2,3]   
A =
     1     2     3
>> A = [1,2,3;4 5 6;7,8 9]
A =
     1     2     3
     4     5     6
     7     8     9
>>

Bonus 2:

Using i and j is bad. See - Using i and j as variables in Matlab

来源：https://stackoverflow.com/questions/25225498/how-to-loop-two-vectors-in-matlab

标签

matlab

loops

for-loop

octave