how to find maximum value of a column,which satisfies a condition.

hi.. suppose i have a matrix as given below

    x          f1         f2      rank

    0.0002    0.0000    3.9991    1.0000
    0.7672    0.5886    1.5198    1.0000
    1.0987    1.2071    0.8124    1.0000
    1.1767    1.3845    0.6779    1.0000
    2.4407    5.9572    0.1943    1.0000
   -0.2008    0.0403    4.8434    2.0000
    3.0549    9.3324    1.1128    2.0000
    3.5944   12.9199    2.5422    3.0000
    4.0472   16.3800    4.1911    4.0000
   -4.6946   22.0392   44.8175    5.0000

here x,f1,f2,rank represents 1st,2nd,3rd,4th columns respectively of the above matrix.

i want to find maximum value and minimum value of 'f1' column whose 'rank'=1 i.e, my answer should be max.value=5.9572,min.value = 0.0000

similarly max.value and min.value of 'f2' column whose 'rank'=1;i.e, my answer should be

max.value = 3.9991;min.value= 0.1943

is there a method to find out without using loops .

Thank you

with regards,

Chandradhar Savanth.

Answer 1

[Azzi Abdelmalek]

You can use max and min function. If M is your matrix

f1=M(:,2);
max_f1=max(f1) 
min_f1=min(f1)

% you can do the same for f2

f2=M(:,3);

[Chandradhar Savanth]

hi Azzi Abdelmalek ..Thank you for your response...

But in the condition of finding the max value of 'f1', i also need to include the condition from 4th column i.e, 'rank=1'.

That is max_f1 under the condition that its 'rank(4th column)=1'.

i.e, my answer should be max_f1 = 5.9572; min_f1 = 0.0000

[Azzi Abdelmalek]

idx=M(:,4)==1;
f1=M(:,2);
max_f1=max(f1(idx)) 
min_f1=min(f1(idx))

[Chandradhar Savanth]

It's working..

Thank you

Azzi Abdelmalek