Thursday, 6 June 2013

R: Enter Data in Matrix Format

Matrix in R is constructed using matrix, rbind, or cbind function. These functions have the following descriptions:
• matrix - used to transform a concatenated data into matrix, of compatible dimensions;
• rbind - short for row bind, that binds a concatenated data points of same sizes by row;
• cbind - short for column bind, that binds a concatenated data points of same sizes by column.
Example 1. Consider this matrix, $\left[\begin{array}{ccc} 3&4&5\\ 2&1&3\\ 6&5&4 \end{array}\right]$. Using the matrix function, we can code this as

So here's what happened above, first the data was concatenated using the c function into a data.a object. Next, we transformed this into a matrix of compatible dimension, that is $3\times 3$. Below are the description of the arguments:
• data.a - the data
• nrow - the number of rows
• ncol - the number of columns
• byrow - the orientation of how data is wrapped into a matrix. If TRUE, then it's row-wise, otherwise, column-wise.
Let's try the rbind for the same data, this is how you do it

Notice the names of the rows are retained in the output? To get rid of this, try

What about the cbind function?