Reducing equations using R - r

Question

I've got this small snippet for reducing a large system:
# set up the multipliers
g1 = (s+9)/((s)*(s+6)*(s+12)*(s+14))
g2 = ((6)*(s+9)*(s+17))/((s+12)*(s+32)*(s+68))
h1 = 13
h2 = 1/(s+7)
# reduce the system in parts
s1 = (g2)/(1 + (g2)*(h1))
s2 = (s1)*(g1)
s3 = (s2)/(1 + (s2)*(h2))
# now we have a unity feedback
g = s3
show(g)
g should be the reduced equation from doing the operations above. However, I get a bunch of errors when I run the code:
Error : object 's' not found
Error : object 's' not found
Error : object 's' not found
Error : object 'g2' not found
Error : object 's1' not found
Error : object 's2' not found
Error : object 's3' not found
Error : error in evaluating the argument 'object' in selecting a method for function 'show': Error: object 'g' not found
Am I not using equations correctly?
edit: my intentions are to have s as a free variable

Answer 1

In order to evaluate your first line of code, there must be an object s that is already defined.
It sounds like your goal is to create a function that outputs g from a single input s. The below code wraps your calculations in a function called make_g:
make_g <- function(s){
# set up the multipliers
g1 = (s+9)/((s)*(s+6)*(s+12)*(s+14))
g2 = ((6)*(s+9)*(s+17))/((s+12)*(s+32)*(s+68))
h1 = 13
h2 = 1/(s+7)
# reduce the system in parts
s1 = (g2)/(1 + (g2)*(h1))
s2 = (s1)*(g1)
s3 = (s2)/(1 + (s2)*(h2))
# now we have a unity feedback
g = s3
g
}
Now, you can call the functions using whatever value for s you like:
make_g(s = 1)