overly convoluted elseif condition

Asked by Nafila Farheen on 15 Nov 2019 at 15:22

Latest activity Answered by Steven Lord on 15 Nov 2019 at 15:57

Accepted Answer by Bob Nbob

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Hi, I am writing a code that uses too many else if conditions.I am wondering is there an easy way to that.

function y=gain(x)

for jj=1:4

p(jj)=1-jj/128;

end

if x==1

y=p(1);

elseif x==2

y=p(2)

elseif x==3

y=p(3);

elseif x==4

y=p(4);

else y==1;

end

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3 Answers

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Answer by Bob Nbob on 15 Nov 2019 at 15:29

Accepted Answer

You can replace all of them with a single statement and indexing.

if x>=1 & x<=4
    y = p(x);
else
    y = 1;
end

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Answer by ME on 15 Nov 2019 at 15:31

function y=gain(x)
  for jj=1:4
    p(jj)=1-jj/128;
  end
  if x<=4
    y=p(x);
  else
    y=1;
  end
end

I have assumed here that your final y==1 was supposed to assign y=1 if x is anything else that 1-4. If that is incorrect then just adjust that last part.

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Answer by Steven Lord on 15 Nov 2019 at 15:57

The approaches suggested by Bob Nbob and ME each work if the only values x can take in the range [1, 4] are integer values. If it can take values like 2.5 or pi, I'd use ismember.

% Sample data
x = [1, 2, 2.5 pi, 4, 42]
p = x.^2 + x
% Locate values of x that are 1, 2, 3, or 4
M = ismember(x, 1:4)
% Start y off with the default value of 1 and the right size (the same size as x)
y = ones(size(x))
% Fill in the elements of y where x is 1, 2, 3, or 4 with the right elements of p
y(M) = p(M)
% Let's do something with the other elements too to illustrate the technique
y(~M) = x(~M)

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