How can I sort an array of repeating elements

Hi

I have the following array (20 by 2). The 1st column is node number and 2nd is temperature. The temperature is in descending order. There are 6 different values of temperatures. How can I sort this array such that it outputs;

set1 temp=670K nodes=10,14,15

set2 temp=668K nodes=385,431,432,440,441,442

set3 temp=655K nodes=649,650,959,960,961

set4 temp=654K nodes=80

set5 temp=653K nodes=89,90,651,652

set6 temp=646K nodes=646

ARRAY:

        10  670.0
        14  670.0
        15  670.0
       385  668.0
       431  668.0
       432  668.0
       440  668.0
       441  668.0
       442  668.0
       649  655.0
       650  655.0
       959  655.0
       960  655.0
       961  655.0
        80  654.0
        89  653.0
        90  653.0
       651  653.0
       652  653.0
        79  646.0

I hope the above is clear. Let me know if its not.

Thanks in advance.

Mohan

[Image Analyst]

I assume that array that you show is the desired output array and the input array - the one you want to sort - is that array but with all the rows in random/arbitrary order.

[mohan]

Hi

It is actually the other way round. input is 20x2 array and the desired output is the one given above the 20x2 array.

Mohan

[Image Analyst]

So the output is a cell array of strings:

ca{1} = 'set1 temp=670K nodes=10,14,15'
ca{2} = 'set2 temp=668K nodes=385,431,432,440,441,442'
ca{3} = 'set3 temp=655K nodes=649,650,959,960,961'
ca{4} = 'set4 temp=654K nodes=80'
ca{5} = 'set5 temp=653K nodes=89,90,651,652'
ca{6} = 'set6 temp=646K nodes=646'

or if you don't actually want to store those strings, then just print them out to the command line or a text file? Please define exactly what and where "outputs" means.

[mohan]

Hi

The exact outputs I require is:

OUTPUT 1: group the nodes to sets but only when there are more than 1 node. see below.

*Nset, nset=set1

10, 14, 15

*Nset, nset=set2

385, 431, 432, 440, 441, 442

*Nset, nset=set3

649, 650, 959, 960, 961

*Nset, nset=set4

89, 90, 651, 652

OUTPUT 2: now combine the above information and temperature data and single node values. see below.

set1, 670

set2, 668

set3, 655

80, 654

set4, 653

79, 646

I hope the above is clear. Please get back to me if not.

Thanks

Mohan

Answer 1

[Image Analyst]

Did you try sortrows():

% Sort by column 2 in descending order.
sortedArray = sortrows(ARRAY, -2)

Answer 2

[Brian B]

It depends how you want to store the sets. If you are comfortable with cell arrays, you can create one vector with the unique temperatures, and then create a cell array of the same size such that each cell has the set of nodes withe the corresponding temperature:

 temperatures =  unique(ARRAY(:,2));
 nodes = arrayfun(@(temp)ARRAY(ARRAY(:,2)==temp, 1),temperatures,'UniformOutput',0)

Answer 3

[Andrei Bobrov]

a = [10  670.0
14  670.0
15  670.0
385  668.0
431  668.0
432  668.0
440  668.0
441  668.0
442  668.0
649  655.0
650  655.0
959  655.0
960  655.0
961  655.0
80  654.0
89  653.0
90  653.0
651  653.0
652  653.0
79  646.0];

[b, ~, c] = unique(a(:,2),'stable');
out = [num2cell((1:max(c2))') num2cell(b) accumarray(c2,a(:,1),[],@(x){x})];