I have a huge vector. I have to count values falling within certain ranges. the ranges are like 0-10, 10-20 etc. I have to count the number of values which fall in certain range.
I did something like this :
for i=1:numel(m1)
if (0<m1(i)<=10)==1
k=k+1;
end
end
Also:
if not(isnan(m1))==1
x=(0<m1<=10);
end
But both the times it gives array which contains all 1s. What wrong am I doing?
You can use logical indexing. Observe:
>> x = randi(40, 1, 10) - 20
x =
-2 17 -12 -9 -14 -14 15 4 2 -14
>> x2 = x(0 < x & x < 10)
x2 =
4 2
>> length(x2)
ans =
2
and the same done in one step:
>> length(x(0 < x & x < 10))
ans =
2
to count the values in a specific range you can use ismember,
if m1 is vector use,
k = sum(ismember(m1,0:10));
If m1 is matrix use k = sum(sum(ismember(m1,0:10)));
for example,
m1=randi(20,[5 5])
9 10 6 10 16
8 9 14 20 6
16 13 14 7 11
16 15 4 12 14
4 16 3 5 18
sum(sum(ismember(m1,1:10)))
12
Why not simply do something like this?
% Random data
m1 = 100*rand(1000,1);
%Count elements between 10 and 20
m2 = m1(m1>10 & m1<=20);
length(m2) %number of elements of m1 between 10 and 20
You can then put things in a loop
% Random data
m1 = 100*rand(1000,1);
nb_elements = zeros(10,1);
for k=1:length(nb_elements)
temp = m1(m1>(10*k-10) & m1<=(10*k));
nb_elements(k) = length(temp);
end
Then nb_elements contains your data with nb_elements(1) for the 0-10 range, nb_elements(2) for the 10-20 range, etc...
Matlab does not know how to evaluate the combined logical expression
(0<m1(i)<=10)
Insted you should use:
for i=1:numel(m1)
if (0<m1(i)) && (m1(i)<=10)
k=k+1;
end
end
And to fasten it up probably something like this:
sum((0<m1) .* (m1<=10))
Or you can create logical arrays and then use element-wise multiplication. Don't know how fast this is though and it might use a lot of memory for large arrays.
Something like this
A(find((A>0.2 .* (A<0.8)) ==1))
Generate values
A= rand(5)
A =
0.414906 0.350930 0.057642 0.650775 0.525488
0.573207 0.763477 0.120935 0.041357 0.900946
0.333857 0.241653 0.421551 0.737704 0.162307
0.517501 0.491623 0.016663 0.016396 0.254099
0.158867 0.098630 0.198298 0.223716 0.136054
Find the intersection where the values > 0.8 and < 0.2. This will give you two logical arrays and the values where A>0.2 and A<0.8 will be =1 after element-wise multiplication.
find((A>0.2 .* (A<0.8)) ==1)
Then apply those indices to A
A(find((A>0.2 .* (A<0.8)) ==1))
ans =
0.41491
0.57321
0.33386
0.51750
0.35093
0.76348
0.24165
0.49162
0.42155
0.65077
0.73770
0.22372
0.52549
0.90095
0.25410
(0<m1(i)<=10)==1gives all ones, I thought a comment in order... MATLAB will evaluate this as follows: firstly0<m1(i)(is m1(i) greater than zero?) is evaluated, the result is0or1(true or false) secondly, using this result,result<=10is evaluated (is 0 or 1 less than or equal to 10?) which will always be true giving1, then1==1is evaluated which will always be true giving the result of1you are consistently getting