Formatting a table in R with special symbols in columns

Question

So I have run some analysis in R which I store in a data.frame() and at the end of the program I want to print a table for the user that is easy to read. I could just return the data frame to the user but I want to have column header names with space or special character (in particular I want there to be a percent sign). So my thought was that I could use the print() or paste() function to output a sort of table format.

So at the end of running the code I want the output to look exactly like the following:

     X       Y   P/E%
0.66120836 0.379 0.99
0.57320298 0.028 0.50
0.77160759 0.024 0.96
0.01532545 0.565 0.37
0.96046884 0.066 0.77

Here is some example code to generate the data I want to output:

x = runif(5)
y = round(runif(5),3)
z = round(runif(5),2)

Now I could use the data.frame() command but it won't allow me a column header like P/E% , for example

A = data.frame(X=x,Y=y,PE=z)

Because it won't like the / or the % sign. The closet thing I could think up to solve the problem is the following:

temp = paste("X","Y","P/E% \n",sep=" ")
for(i in 1:5){
    temp = paste(temp,paste(x[i],y[i],z[i],"\n",sep=" "),sep=" ")
}

but the spacing is weird if the column headers are long or the number of digits are different. If I go with the paste option, which I like, is there a way to make it so that the columns are aligned nicely no matter the shape of the data or number of digits? Like a left or right align?

Lastly, this code is going into an R shiny app and so it would be very nice to be able to solve this problem without having to have the user load a package to solve it.

Answer 1

Column names can have special symbols in them if they are quoted (if you disable validity checking of column names):

A = data.frame(X=x, Y=y, 'P/E%'=z, check.names=FALSE)

You then need to always use quotes with $ calls for access. $ accept any of the three types of quotes as long as they are matched:

a$`P/E%`

The "[[" function is designed to handle quoted arguments, but do not use backticks:

A[['P/E%']]

If you have an actual use case in mind, it needs to be presented more completely than just saying "needs to work with Shiny".