Finding ranges 2to5, 5to10 and 10to20 out of large values in a large array.

Question

Syed Zohaib Ali 2012-12-4

0
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https://ww2.mathworks.cn/matlabcentral/answers/55662-finding-ranges-2to5-5to10-and-10to20-out-of-large-values-in-a-large-array

Hi Guys

I have a Question about finding different ranges e.g 2 to 5, 5 to 10 and 10 to 20, within a large array .

I have an array 'DOP' of dimension 1x86400 that contains values between 0 and 1.4804e+05. I wanted numbers between 0 to 20 within that array so this range found by a condition

if (DOP(j)<=20);

DOPj(j)=j;

end

eles

'check on another iteration'

within while loop. Here j is the time at which DOP<=20. So DOPj contains the times values at which DOP<=20 and 0s at times where there is no DOP<=20. So DOPj also has same dimension as DOP i.e. 1x86400.

 Now I have a new array DOPj of same dimension but with values of times at which we have DOP<=20 and 0s at times where there is no values DOP<=20.

I discarded 0s in DOPj by

[i20 j20]=find(DOPj);

Now j20 has only times at which DOP<=20. Length(j20) gives 39961. That means out of 86400 values of DOP I have 39961 values that of DOP<=20.

Now I can find the indices of DOP at which I can have different ranges 2 to 5, 5 to 10 and 10 to 20 by

[i25 j25]=find(DOP(j20)>=2 & (DOP(j20)<=5));

[i510 j510]=find(DOP(j20)>=5 & (DOP(j20)<=10));

[i1020 j1020]=find(DOP(j20)>=10 & (DOP(j20)<=20));

length(j25) gives 18423

length(j510) gives 14442

length(j1020) gives 7096

and

length(j1020)+length(j510)+length(j25) gives 39961, which looks great.

But unfortunately max(DOP(j25)) gives 1.4593e+04 and min(DOP(j25)) gives 0, which is totally wrong as I need range 0 to 5.

similarly, max(DOP(j510)) gives 58.1935 and min(DOP(j510)) gives 0. Also max(DOP(j1020)) gives 159.3996 and min(DOP(j1020)) gives 0, which are all wrong,

Could someone help me out what I am doing wrong?

Thanks in advance.

Zohaib