Alike Objects/Functions in R

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Matrix VS Data Frame:

1. The data in a matrix must be of the same type while different columns in a data frame can have different types.

2. A data frame is much bigger than a matrix with the same dimension. If possible, always use matrix instead of data frame to do computation. Especially, when you creating arrays using the function array, you should avoid using a data frame as the data source (even if all columns of the data frame have the same type). A way to work around this is to first convert a data frame to a matrix and then use the matrix as the data source.

3. A data frame has names for rows and columns by default while a matrix not.

sub VS gsub

1. The function sub substitute only the first occurence of the string that matches the given pattern while function gsub substitute all occurences of strings that matches the given pattern.

warning VS warnings

1. The function warning shows a user-defined warning message while the function warnings displays previously generated warning messages.