Getting error matrix dimensions must agree when I run a stack that calculates the sin of the last number on the stack.

i have a rpmcalcuator stack that only takes certain operands. sin is one of them. when i try to add sin to my stack, it gives me an error.

i am attaching both files. stackmain runs rpm calc. if you could help me figure out how to code my sin function i would appreciate it.

Answer 1

[Geoff Hayes]

Nicole - a helpful statement to run before executing your code is dbstop if error. This will cause the code to pause at the line that is generating the error message. In your case, the error occurs at

 elseif (x == 'pi')

because you are comparing a string of length three (for sin) versus a string of length two (for pi).

When doing string comparisons, you should use strcmpi. So your above line of code now becomes

 elseif strcmpi(x,'pi')

Do the same for the comparison with 'e' and try running through the code again.

EDIT

Once you fix the above, you will notice an error at line 94 of RPMCalculator

 self.push(num2str(sin(self.data(self.top-1),u)));

because the variable u is undefined. Since sin only takes one input, you can remove this.

[Nicole]

that worked. thank you so much!

[Geoff Hayes]

No problem!

[Nicole]

if you don't mind, i do have another question. i forgot to ask.

The matlab screen prints out stuff I don't want it to but I don't know how to stop it. i have ; everywhere I don't want it to print but it continues to print out

/

ans =

RPMCalculator with no properties.

sin

ans =

RPMCalculator with no properties.

How do i stop that?

[Geoff Hayes]

Typically, the unexpected output occurs (especially when written to the Command Window as ans) occurs on lines of code that aren't terminated with a semi-colon. In this case, one is needed at the end of line 44 (in RPMCalculator.m)

 else
    self.math(x);   % <--- semi-colon needed here
 end

The +, sin, and / occur because of the disp at line 83 in the math function

 function [self] = math(self, x)
    disp(x)
    switch x

[Nicole]

I put ; in more places and it suppressed the

ans =

RPMCalculator with no properties.

It is still printing out my case strings. if i put a = or + it will show that. I put ; after each case argument. is it the way i am calling it out? it's not the worst thing in the world but it's bugging me.

[Geoff Hayes]

Hi Nicole - I think it is because of the disp(x) in the math function that the + or sin or - is appearing. You shouldn't need to put semi-colons after the case argument. As soon as I commented out the disp(x) line, the only output in the Command Window (when running your original StackMain is

 d (i) = 
    12

 The last 3 values on the stack are:  
     4
     3
    12