matlab cant divide using /

Question

I have some simple function that takes in a value

This value is the checked off a number of if or elseif statements to calculate another value.

The problem is it seems to find an error when trying to run which says

Error using / Matrix dimensions must agree.

Error in abc (line 9) a = 5000 / g;

the code is as follows

function abc(g)


if (g == 100)
   a = 1;
elseif (g <= 99 & g >= 50)    
   a = 200 -2*g;
elseif (g <= 50 & g >= 1)
   a = 5000 / g;
else
  warning('Invalid value passed, a defaults to 1');
  a =1;
end
end

So, im passing in abc 100 and i expect a to be 1 but instead it runs through each if / elseif and throws an error on a = 5000/g

I should also mention that i initially tried using && in the elseifs but this also gave an error which said

Operands to the || and && operators must be convertible to logical scalar values.

Error in abc (line 6) elseif (g <= 99 && g >= 50)

Anybody any idea whats going on here ? Thanks

Answer 1

You are probably passing a matrix to your function, e.g. when you call

abc(yourdata)

yourdata is actually not one number, but a matrix. If you called directly

abc(100)

you should not see your problem (or do you?).

In other words, your main problem is not inside your function, but when you call it!

Given your description, it seems that you set yourdata(1) to the value 100 that you want to test, but some other element of the matrix has a different value, which is why the if construct branches into the else case. There, you need ./ instead of / if you want to do element-wise division instead of matrix division.

But really you probably just need to make sure that yourdata is scalar when you call your function.