MATLAB: Help me avoid this error: Empty matrix: 0-by-1

empty matrix: 0-by-1

I have a program like this:
clc
a=[0 0; 150 0.5; 300 0.35; 450 0.253; 600 0.22; 750 0.276; 900 0.183; 1050 0.228; 1200 0.17; 1350 0.207; 1500 0.2; 1650 0.19; 1800 0.187; 1950 0.21; 2100 0.176; 2250 0.197; 2400 0.17]
b=[900 900 750 2100 750 150 150 150 300]'
    for i=1:5
        c=find(a(:,1)==b(i));
        f=a(c,:);
        d(i)=prod(f);
    end
e=sum(d)
My main program for many vectors b with components of a. I want to find e, but few result of c are Empty matrix: 0-by-1
Help me. Thanks.

Best Answer

Change : d(i) = prod(f); to
 if isempty(f)
  d(i) = NaN;
 else
  d(i) = prod(f);
 end
and e = sum(d) to:
 e = nansum(d);
If NaN isn't convenient, change it for something that is.
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