Find the length of a vector up to a certain value

Hi!

I have a vector (SortN1250) which is 75558x1 with a range from 1:1000 and i want to extract the length of the vector at certain values (100:100:5000) and ad them to another vector. This is my code:

ProbdistPoredens(50,1)=zeros
for n=100:100:5000
    ind = find(abs(SortB1250(:,1)<n));
    lengthind=length(ind)
    for i=1:50
        ProbdistPoredens(i,1)=lengthind
    end
end

ProbdistPoredens is however just filled with the number 75558 on all 50 rows. This number is only expeted to show at the very last row in the column.

Any suggestions would be greatly appriciated!

Regards,

[Torsten]

length(ind) is just one value (in your case 75558), not an array.

[Holmbrero]

But ind should change with n, right?

Answer 1

[Image Analyst]

Explain in words what this means: (100:100:5000)

Do you want only elements that have values of 100, 200, 300, 400, ..., 4900, or 5000?

Is that what "at certain values" means? Or does it mean at certain indexes?

[Holmbrero]

I want only elements that are smaller than that value. 100 is the first value in the vector where I want to find the length. 200 is the next and 5000 is the last. I guess the actual index would do just as fine.

The value for 200 should be the value of the length of the indexes between 1:100 plus the value of the length of the indexes between 100:200.

[Image Analyst]

Try this:

% Create sample data.
SortB1250 = 1000 * rand(75558, 1);
ProbdistPoredens=zeros(50,1);
n = 100 : 100 : 5000

n = 1×50

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500 2600 2700 2800 2900 3000

for k = 1 : length(n)
    ind = find(SortB1250 < n(k));
    ProbdistPoredens(k) = length(ind);
end
plot(ProbdistPoredens, 'b.-', 'lineWidth', 2)
grid on;

[Holmbrero]

Works great, thank you!

Answer 2

[Simon Chan]

The inner for loop is not necessary and it overwrite itself for every 'n'.

You may modify the code as follows.

ProbdistPoredens(50,1)=zeros;
for n=100:100:5000
    ind = find(abs(SortB1250(:,1)<n));
    lengthind=length(ind);
    ProbdistPoredens(n/100,1)=lengthind;                % modify the index from i to n/100
end

Alternatively, you can use function histcounts to do the same thing.

[ProbdistPoredens,~] = histcounts(SortB1250,0:100:5000,'Normalization','cumcount')   % Use function hiscounts