MATLAB: How to extract unique values associated with repeated values in another column

for loop

I have monthly climate data, and I've copied a subset below. The first column has values that repeat from 1 to 12 (months), and the second column has unique precipitation values. How do I extract the ppt values for each individual month and put in a separate vector? For example, how do I extract the ppt values associated with value 1, and then create a separate vector. With the dataset below, the new vector would only have two rows, since the monthly value of 1 only repeats twice. My full dataset has 122 repetitions. I would like to write a forloop for this.
    month    ppt
    1.0000  344.6000
    2.0000   92.1900
    3.0000  170.0400
    4.0000   32.8000
    5.0000   30.0400
    6.0000         0
    7.0000         0
    8.0000         0
    9.0000   10.6500
   10.0000   12.5400
   11.0000   43.0900
   12.0000   38.7300
    1.0000  297.5600
    2.0000   13.1100
    3.0000  168.8700
    4.0000   87.6600
    5.0000   51.0700
    6.0000         0
    7.0000    1.0900
    8.0000    6.7100
    9.0000    6.2600
   10.0000   50.9100
   11.0000  109.7800
   12.0000   93.0600

Best Answer

mp = [
  1.0000  344.6000
  2.0000   92.1900
  3.0000  170.0400
  4.0000   32.8000
  5.0000   30.0400
  6.0000         0
  7.0000         0
  8.0000         0
  9.0000   10.6500
 10.0000   12.5400
 11.0000   43.0900
 12.0000   38.7300
  1.0000  297.5600
  2.0000   13.1100
  3.0000  168.8700
  4.0000   87.6600
  5.0000   51.0700
  6.0000         0
  7.0000    1.0900
  8.0000    6.7100
  9.0000    6.2600
 10.0000   50.9100
 11.0000  109.7800
 12.0000   93.0600];
month = mp(:,1);
ppt = mp(:,2);
results = accumarray(month, ppt, [12 1], @(V) {V.'});
In the special case where each month has the same number of entries, you can then proceed to
vertcat(results{:})
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