I am having some difficulty in using the function else in R.
When I input ?else, I didn't get any help about the function else.
When I run the following program:
i=1
if(i>1){print("aa")}
else{print("bb")}
the else didn't work. Can someone tell me the reasons?
to get help type
?'else'
look at the paragraph in help
Note that it is a common mistake to forget to put braces ({ .. }) around your statements, e.g., after if(..) or for(....). In particular, you should not have a newline between } and else to avoid a syntax error in entering a if ... else construct at the keyboard or via source. For that reason, one (somewhat extreme) attitude of defensive programming is to always use braces, e.g., for if clauses.
if(i>1){print("aa")
}else{print("bb")}
or
if(i>1){print("aa")}else{print("bb")}
will presumably work for you.
i=1
{
if(i>1){print("aa")}
else{print("bb")}
}
would also work. The key is to let the parser know to expect more input.
Related
I have a command with six lines that I want to use several times. Therfore, I want to assign a name to this command and use it as a procedure instead of writing the whole command lines over and over.
In this case it is a <-rbind() command, but the issue is also more general.
modelcoeff<-rbind(modelcoeff,c(as.character((summary(mymodel)$terms[[2]])[[3]]),
as.character((((((summary(mymodel)$terms[[2]])[[2]])[[3]])[[3]])[[2]])[[3]]),
summary(mymodel)$coefficients[2,1],
summary(mymodel)$coefficients[2,4],
summary(mymodel)$coefficients[2,2],
summary(mymodel)$r.squared*100))
I would like to call something like rbindmodelcoeff and execute these command lines. How can I achieve this?
I tried to write a function, but it didn't seem to be the right approach.
A literal wrapping of your code into a function:
rbindmodelcoeff <- function(modelcoeff, mymodel) {
rbind(modelcoeff,
c(as.character((summary(mymodel)$terms[[2]])[[3]]),
as.character((((((summary(mymodel)$terms[[2]])[[2]])[[3]])[[3]])[[2]])[[3]]),
summary(mymodel)$coefficients[2,1],
summary(mymodel)$coefficients[2,4],
summary(mymodel)$coefficients[2,2],
summary(mymodel)$r.squared*100))
}
However, there are a couple changes I recommend:
call summary(mymodel) once, then re-use the results
you are using as.character on some of the objects but not all within the enclosing c(.), so everything is being converted to a character; to see what I mean, try c(as.character(1), 2); we can use a list instead to preserve string-vs-number
rbindmodelcoeff <- function(modelcoeff, mymodel) {
summ <- summary(mymodel)
rbind(modelcoeff,
list(as.character((summ$terms[[2]])[[3]]),
as.character((((((summ$terms[[2]])[[2]])[[3]])[[3]])[[2]])[[3]]),
summ$coefficients[2,1],
summ$coefficients[2,4],
summ$coefficients[2,2],
summ$r.squared*100))
}
But there are still some problems with this. I can't get it to work at the moment since I don't know the model parameters you're using, so as.character((summ$terms[[2]])[[3]]) for me will fail. With that, I'm always hesitant to hard-code so many brackets without a firm understanding of what is being used. It's out of scope for this question (which is being converting your basic code into a function), but you might want to find out how to generalize that portion a bit.
I have a function that validates a url based on input from a user. The way the function is set up, if the url doesn't validate (either because it doesn't exist or because it is a duplicate) the function simply ends.
How do I make it so that if the url isn't validated, the user goes back to the input dialogue to start the validation process over again instead of just ending the function?
exfun <- function(){
x <- toupper(readline("Do you want to do the function? Y/N......."))
if (x == "Y"){
writeLines("This is where the function body would be, but it's huge so for the sake of this StackExchange question, we'll just make it a simple thing")
} else
writeLines("Well then why did you start the function? We'll try this again")
#This is where I would like the function to return to the "x<-...." line.
There are a few places where I would like to be able to "return to line X" as there are at least two validation points. I have it set up as a series of if else arguments which else into a message. How can I make it else into a message and bring the user back to the beginning/a previous validation test?
I fiddled with the repeat function, but couldn't get it to return from if else correctly.
I'm not really answering your question, but I'll give you an example that might help you (and probably someone will give a hint to improve this).
You can set a while loop and put conditions to continue the loop or to end it, simply like this:
i <- 1
while (T) {
print(i)
i <- i + 1
if (i==5) {
print("NEXT")
next
}
if (i==10) break
}
As you see, the if with next conditions do something in your code, and keep running it after the command print("NEXT"). Also, the break is inside a condition to stop your loop.
I hope it helps, because with your example is difficult to give a full answer.
I'm trying to package some code I use for data analysis so that other workers can use it. Currently, I'm stuck trying to write a simple function that imports data from a specific file type generated by a datalogger and trims it for use by other functions. Here's the code:
import<-function(filename,type="campbell",nprobes){
if (filename==TRUE){
if (type=="campbell"){
message("File import type is from Campbell CR1000")
flux.data<<-read.table(filename,sep=",",header=T,skip=1)
flux.data<<-flux.data[,-c(1,2)];flux.data<<-flux.data[-c(1,2),]
if (nprobes=="missing"){
nprobes<-32
}
flux.data<<-flux.data[,c(1:nprobes)]
flux.data.names<<-colnames(flux.data) #Saves column names
}
}
}
Ideally, the result would be a dataframe/matrix flux.data and a concomittant vector/list of the preserved column headers flux.data.names. The code runs and the function executes without errors, but the outputs aren't preserved. I usually use <<- to get around the function enclosure but its not working in this case - any suggestions?
I think the real problem is that I don't quite understand how enclosures work, despite a lot of reading... should I be using environment to assign environments within the function?
User joran answered my question in the comments above:
The critical issue was just in how the function was written: the conditional at the start (if filename==TRUE) was intended to see if filename was specified, and instead was checking to see if it literally equaled TRUE. The result was the conditional never being met, and no function output. Here's what fixed it:
import<-function(filename,type="campbell",nprobes){
if (exists(filename){
if (type=="campbell"){
#etc....
Another cool thing he pointed out was that I didn't need the <<- operator to utilize the function output and instead could write return(flux.data). This is a much more flexible approach, and helped me understand function enclosures a lot better.
Is there a way to "die" in execution flow in an xquery file and output a nicely formatted printout of a sequence variable?
I'm trying something like:
return { fn:error(xs:QName("ERROR"), $xml) }
but that doesn't quite seem to work.
Thanks!
Based on your comment (you need it for debugging) I guess you are looking for the fn:trace function, described here http://www.xqueryfunctions.com/xq/fn_trace.html
If you want to abort the execution flow and output an error in your application you should in fact use the XQuery exception handling.
Try something like this, omitting the return if this isn't part of a FLWOR expression.
...
return fn:error((), "DEBUG", $xml)
There's no need for curly braces unless you're enclosing an expression, for example <x>{ current-time() }</x>. The return expression is not enclosed.
With MarkLogic it's best to leave the first parameter of fn:error empty. That way you don't have to worry about a QName, and anyway some folks believe that it's reserved for predefined errors. MarkLogic uses the second parameter to fill in error:code, and the third parameter for data.
For more on fn:error, see http://docs.marklogic.com/fn:error and https://github.com/robwhitby/xray/pull/11
I have problem in using if else inside function, my code is like this:
ConvertWgtZooLS <- function(WgtZoo, LSWay, Pos){
If(LSWay == 0){
NewWgtZoo <- WgtZoo
}else{
BackPos <- BackMatrix(Pos,1)
NewWgtZoo<- Ifelse((Sign(WgtZoo) * Sign(BackPos) * LSWay)>=0, WgtZoo, 0)
}
return(NewWgtZoo)
}
However, when I run that in R, error message appears as:
"Error: unexpected '{' in:
"ConvertWgtZooLS <- function(WgtZoo, LSWay, Pos){
If(LSWay == 0){"
How can I resolve this? What is the syntax problem there? I checked many websites and seems the above if else syntax is correct.
Thanks a lot!
The error in your code is that you have used If instead of if, and R is case-sensitive. Thus, it is possible to have another function named If that does something different from if, and, as #danielkullmann points out, that function is exactly what R is looking for.
The error messages that R produces are not always the most helpful, but in this case, it does point you very close to the problem area. It shows you where it got "confused" but it's up to you to figure out why!
After you've fixed that first problem, you'll find another one (for the same reason) on line 6, where you have written Ifelse instead of ifelse.
One last point: R is pretty whitespace friendly, so it is good practice to leave some space in your code to help improve legibility, particularly with if and else statements. Here's why:
I find if (LSWay == 0) { easier to read than if(LSWay == 0){
When using an actual function, like sum(x), you do not usually add a space, making it easier to spot these conditional statements in large blocks of code.
The Google R Style Guide is an interesting read in this regard.