[R] Formatting column displays

[Bruce Ratner PhD]

R-helpers:
I need some references for formatting the display of my data frame columns. 
Any guidance will be appreciated. Bruce
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I have a date frame with one column as an integer for which I want a comma display, 
one column consisting of dollar amounts, one column for which I want a display to two digits after the decimal point, and one column as integers ranging between 
100 - 999.