Using for loop for arrays
显示 更早的评论
I have an array that includes a list of temps, and I am trying to count the temps less than 75. This is the code I used -
clc;
clear;
close all;
count=0;
a = [45, 56, 66, 78, 54, 67, 56, 88, 95, 93, 23, 56, 78, 45, 67, 56, 34, 67, 87, 64, 94, 57, 61, 24]; %16 below 75
for i = 1 : length(a)
if i < 75
count = count+1;
end
end
disp(count)
Not sure what is wrong. I am not able to get the desired output. Any help?
采纳的回答
Not sure what is wrong
You'll always going to get min(74, numel(a)) as a count, since you're comparing the index i instead of the value a(i) to 75.
Note that as usual in matlab, there's no need for a loop for this
count = nnz(A < 75)
%or
count = sum(A < 75)
2 个评论
Archit Muchhal
2019-8-30
Guillaume
2019-8-30
Well, yes, if you look at any matlab code (or for that matter code in other languages), they never use the syntax low<x<high. That's because it doesn't do what you want.
low < x < high first compares low to x and returns a logical vector of 0 and 1. it then compares this logical vector of 0 and 1 to high. So if high is greater than 1 the final result is just a vector of 1. Just as you get. The proper syntax is low < x & x < high.
So
count2 = sum(75<a & a<95);
%etc.
Note that numbered variables are universally a bad idea. Rather than embedding the index into the variable, use proper indexing:
count(1) = nnz(a < 75);
count(2) = nnz(75 < a & a < 95); %what about if a is 75?
count(3) = nnz(95 < a & a < 105); %or 95?
count(4) = nnz(a > 105); %or 105?
count = histcounts(a, [-Inf, 75, 95, 105, Inf])
更多回答（0 个）
类别
在 帮助中心 和 File Exchange 中查找有关 Matrix Indexing 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
