print 函數的打印格式：

##no quote print out
> x <- letters[1:5]
> print(x,quote=F,);print(x,quote=T)
[1] a b c d e
[1] "a" "b" "c" "d" "e"

##print without number of vector and quote
> cat(x)
a b c d e

### ot remove quote of string
> noquote(x)
[1] a b c d e

### to convert a few of string to a string 
> toString(x)
[1] "a, b, c, d, e"

### to remove the space in string
### argument which could be which=c("left","both","right")

> trimws(" x ",which=c("both"))
[1] "x"

print,cat打印格式及字符串引號格式，去掉字符串空格 in R