Getting "Subscript indices must either be real positive integers or logicals" error from simple calculation

When running my code I get the Subscript indices must either be real positive integers or logicals" error.

After some debugging I found where the issue is generated. I have the following variables:

v = 7.1 (readback shows value 7.100000000000000) LOWERVOLTAGE = 7 (readback shows value 7) STEPSIZE = 0.1 (readback shows value 0.100000000000000)

When I run the following code:

Cur_Row = (((v-LOWERVOLTAGE)*(1/STEPSIZE))+1)

I get this as answer:

Cur_Row = 1.999999999999996 (I expected 2)

After this I use Cur_Row to access a matrix and get the error

When I run the code with STEPSIZE = 0.5 I don't get this issue.

I know that I can use a round function as workaround, but I would like to know why this happens

[Adam]

You can just do an online search for floating point arithmetic or similar phrases and you will get links like, e.g

https://en.wikipedia.org/wiki/Floating-point_arithmetic

to explain. Probably not the best link, but then I'm sure you know how to search the internet just as well as I do to find better ones!

[Anthony Fibi]

Ok I understand, please add your comment as answer so I can accept it

Answer 1

[Adam]

You can just do an online search for floating point arithmetic or similar phrases and you will get links like, e.g

https://en.wikipedia.org/wiki/Floating-point_arithmetic

to explain. Probably not the best link, but then I'm sure you know how to search the internet just as well as I do to find better ones!