R help - Feb 2010 - function to display histogram fails to do so when histogram is not the last expression in the function

TestHistogram_A  is a function that plots a histogram,  then returns 3.  For
me it fails 

to display the plot, at least in the order given below.

 

TestHistogram_B is a function that plots a histogram, then exits.   The only
difference between

the 2 functions is that B does not return 3.   It displays the plot.

 

This problem does not occur when histogram is replaced by boxplot

 

Their use is in the following statements:

 

Data <- c(1,1,1,2,2)

Data <- data.frame(Data)

TestHistogram_A <- function (my.data) {
histogram(my.data[,1],main="TEST");
3}

TestHistogram_A(Data)

TestHistogram_B <- function (my.data) {
histogram(my.data[,1],main="TEST") }

TestHistogram_B(Data)

 


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On Feb 17, 2010, at 2:13 PM, Terrence Ireland wrote:
> TestHistogram_A  is a function that plots a histogram,
It creates a plot-description but does not "plot" it.
> then returns 3.  For
> me it fails to display the plot, at least in the order given below
>
> TestHistogram_B is a function that plots a histogram, then exits.    
> The only
> difference between
>
> the 2 functions is that B does not return 3.   It displays the plot.
>
> This problem does not occur when histogram is replaced by boxplot
histogram is a lattice function. Lattice functions return a value  
which is a list describing the plot. This phenomenon is covered in a  
FAQ:

http://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-do-lattice_002ftrellis-graphics-not-work_003f


>
> Their use is in the following statements:
>
> Data <- c(1,1,1,2,2)
> Data <- data.frame(Data)
> TestHistogram_A <- function (my.data) { histogram(my.data[, 
> 1],main="TEST");
> 3}
You have thrown away the histogram in your "_A" function. Boxplot os a
base graphics function which prints by "side-effect" and returns NULL.
If you want to print() the histogram, then do so within your function.
> TestHistogram_A(Data)
> TestHistogram_B <- function (my.data) { histogram(my.data[, 
> 1],main="TEST") }
> TestHistogram_B(Data)
>

David Winsemius, MD
Heritage Laboratories
West Hartford, CT