Debugging user-defined function - r

Question

For a dataset of "Baltimore homicides"
It is required to create a function that takes a string for example "shooting" and return an integer represents the count of victims of "shooting".
I wrote the following function but i receive errors
Error: unexpected '}' in " }"
Error: object 'counti' not found
I also cant figure out if the ==Null is correct
count <- function(cause = NULL) {
## Check that "cause" is non-NULL; else throw error
if cause==NULL
{
stop()
print("no cause provided")
}
## Read "homicides.txt" data file
homicides <- readLines("homicides.txt")
## Extract causes of death
i <- grep(cause, homicides) ##get indices of cause
counti <- lenghth(i) ##get count of indices
## Check that specific "cause" is allowed; else throw error
if counti=0
{
stop()
print("no such cause")
}
## Return integer containing count of homicides for that cause
return(counti)
}
this is my working function after edit, thanks guys
count <- function(cause = NULL) {
if(missing(cause) | is.null(cause)) stop("no cause provided")
homicides <- readLines("homicides.txt")
i=length(grep(cause, homicides))
if(i==0) stop("no cause found")
return(i)
}

Answer 1

You can simplify your function to 2 lines by doing this:
count <- function(cause = NULL, data) {
if(is.null(cause)) stop("no cause provided")
length(grep(cause, data))
}
data <- c("murder", "some other cause")
count("murder", data)
[1] 1
Note the following principles:
R has many features of a functional language. This means that each function should, as far as possible, depend only on the arguments you pass it.
When you have a bug in your code, simplify it to the shortest possible version, fix the bug, then build out from there.
Also, keep stop() for really fatal errors. Not finding a search string in your data isn't an error, it simply means the cause wasn't found. You don't want your code to stop. At most, issue a message() or a warning().