Convert 2 by 2 Contingency Table to Data Frame in R

Contingency tables are useful short hand ways of inputting and visualizing data. I have yet to find an easy way to convert between contingency tables and data frames in R. Below is a short script in which I input a contingency table, create a function to convert the 2 by 2 table to a data frame, and convert the data frame back to a table. These operations are useful for running some statistical operations that either only work on tables or only work on data frames. Hope the below example is useful.

Create Empty Data Frame in R with Specified Dimensions

Sometimes it is necessary to create an empty data frame in R to fill with output.  An example would be output from a for loop that loops over SNPs and calculates an association p-value to fill into the empty data frame.  The matrix functionality in R makes this easy to do.  The code below will create a 100 by 2 matrix and convert it into a dataframe with 100 rows and 2 column variables.  The nrow and ncol options are what designate the size of the resulting data frame.  The data frame is filled with NA values so that missing values are handled appropriately.  Below is some example code: