Check elements of matrix

i have this program

N=1000000;

t=1;

X=rand(1,N);

for i=0:.1:5

y=(X>=i & X<(i+.1));

s(t)=sum(y);

t=t+1;

end

-----------------------------------

so; i need to check all elements of matrix X against each element in matrix i. is there any method to do this without for loop? i.e. by using matrix notation.

Answer 1

[Image Analyst]

Have you realized that you're simply calculating the histogram and that there is a function for that called histc()? Here, do it this way instead:

binEdges = 0 : 0.1 : 5;
counts = histc(X, binEdges);

Here, my counts is the entire histogram, basically the same as your s except that you calculated s for only 5 bins.

If you say " but we're not allowed to use any built-in functions" then please tag this as homework.

Answer 2

[Azzi Abdelmalek]

N=1000000;
X=rand(1,N)*6;
arrayfun(@(x) sum(X(X>x & X<x+1)),1:5)

Answer 3

[Greg Heath]

Matrices can be compared using <, =, or > only if they have the same dimensions or at least one is a scalar.

Note that

X < 1

Therefore

y = 0 for i > 1.

Consequently, the following makes more sense:

t=0

for i=0:0.1:1 % NOT 5

t =t + 1 % Update at beginning of loop

y = ...

s(t) = ...

end

Hope this helps.

Thank you for formally accepting my answer.

Greg

P.S. An alternative is to use 0: 0.1 :5 with X = 5*rand(N)