Difference between paste and print (affecting result of function)

Question

To start off, I'm not really sure what the difference between paste and print is. But I am using "print" to spit out generic statements and "paste" to spit out statements that use/ reference specific variables.

My issue is that when using paste within a function, I am losing my pasted output if there is anything included in the function following the "paste" statement.

Please see the following three functions:

TS<-5

Example 1- everything works fine

T<-function(){

if(exists("TS"))
{paste("TS= ", TS, sep=" ")}

else

if(!exists("TS"))
{print.noquote("No TS Values")}

}

Example 2- My Problem. When I add anything (in this case another print command) following my "if" statement I will lose my pasted output

T<-function(){

if(exists("TS"))
{paste("TS= ", TS, sep=" ")}

else

if(!exists("TS"))
{print.noquote("No TS Values")}

print("my exsistance removes paste output") 

}

Example 3- The same statement placed before the "if" has no negative effect

T<-function(){

print("my exsistance does not remove paste output")

if(exists("TS"))
{paste("TS= ", TS, sep=" ")}

else

if(!exists("TS"))
{print.noquote("No TS Values")}


}

Can someone explain where the conflict is within this function. And better yet how can I work around it so that I can have a paste statement followed by other actions within a function

basically how can I get example #2 to work.

Brownie points- (for sake of visual consistency) when using "print.noquote", is there such a thing as a paste.noquote?

use print, cat, or better yet, message if you want text to be echoed. paste is only used to concatenate strings; it will be echoed as a side-effect iff it is the last statement of a function with no explicit return value. — baptiste
@ttmaccer That wouldn't cause a random paste statement to print to the console though. It's useful if you're printing inside of a loop though... — Dason

mnel mnel · Accepted Answer · 2012-07-18T02:08:39

paste concatenates (pastes) strings and returns a character vector, so you can do thing like

paste('a','b', sep = '-')

## [1] "a-b"

print prints values. From ?print

print prints its argument and returns it invisibly (via invisible(x)). It is a generic function which means that new printing methods can be easily added for new classes.

Most classes will have a defined print method (or will use print.default)

You can see the available print methods by typing

methods('print')

In your case paste("TS= ", TS, sep=" ") returns a character vector, so when this is the result of the function, print.character is used to display the results

In fact, I think you want message not print or print.noquote.

T <- function() {
    if (exists("TS"))
    {
        message(paste("TS= ", TS, sep=" "))
    } else if (!exists("TS")) {
        message("No TS Values")
    }
    message("my exsistance removes paste output") 
}

Difference between paste and print (affecting result of function)

2 Answers