Dr. Mark Gardener

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Tips and Tricks - for R and Excel

On this page you can find tips, tricks and hints for using both R and Excel. At the end of each tip there are links forwards and backwards as appropriate. There is also an index of R tips and an index of Excel tips.

For most analytical purposes the combination of Excel and R is unbeatable! Excel is great as a data management tool and for preparing data for analysis. You can also use it to get an overview of your data or to make simple (and not so simple) graphs. R is an analytical "swiss army knife" and can carry out a mind-boggling array of analytical routines as well as producing great graphics.

Tips & Tricks for R | Tips & Tricks for Excel | An Introduction to R | MonogRaphs | Writer's Bloc


Make a matrix:
matrix()
rbind()
cbind()

Top

Make a matrix

A matrix is a 2D object with rows and columns that contains data all of the same sort, e.g. all numbers or all text. You can make a matrix in various ways:

  • The matrix() command – this splits a vector into rows and columns.
  • The rbind() command – this takes several items and joins them together as rows. You usually join several vectors but you can also use this to join an existing matrix to another matrix or vectors.
  • The cbind() command – this is similar to rbind() but operates over columns.

The matrix() command assumes that the vector of data will split "nicely" into rows and columns; if it doesn't then you may have to add NA items at the end to make it factorise.

> dat = 1:12
> dat
[1] 1 2 3 4 5 6 7 8 9 10 11 12
> matrix(dat, ncol = 3)
[,1] [,2] [,3]
[1,] 1 5 9
[2,] 2 6 10
[3,] 3 7 11
[4,] 4 8 12
> matrix(dat, ncol = 3, byrow = TRUE)
[,1] [,2] [,3]
[1,] 1 2 3
[2,] 4 5 6
[3,] 7 8 9
[4,] 10 11 12

The vector is split column-wise unless you specify that you want to fill row-wise using the byrow = TRUE instruction.

The rbind() and cbind() commands join items as rows or columns:

> d1 = 1:4 ; d2 = 5:8 ; d3 = 9:12
> d1 ; d2 ; d3
[1] 1 2 3 4
[1] 5 6 7 8
[1] 9 10 11 12
> rbind(d1, d2, d3)
[,1] [,2] [,3] [,4]
d1 1 2 3 4
d2 5 6 7 8
d3 9 10 11 12
> cbind(d1, d2, d3)
d1 d2 d3
[1,] 1 5 9
[2,] 2 6 10
[3,] 3 7 11
[4,] 4 8 12

The rows or columns have names taken from the original vector names. You can also use the commands to add rows or columns to an existing matrix, as long as the dimensions are appropriate:

> mat = cbind(d1, d2, d3)
> mat
d1 d2 d3
[1,] 1 5 9
[2,] 2 6 10
[3,] 3 7 11
[4,] 4 8 12
> cbind(mat, d1)
d1 d2 d3 d1
[1,] 1 5 9 1
[2,] 2 6 10 2
[3,] 3 7 11 3
[4,] 4 8 12 4

You can alter the names of the rows and columns afterwards.


Top << Previous Tip: Multi-dimensional objects in R >> Next Tip: Naming rows and columns of a matrix
 
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More links:

An introduction to R

See my Publications about Excel, R, statistics and data analysis Courses in R, data analysis, data management and statistics Visit the R Project website
 

See my Publications about statistics and data analysis.

MonogRaphs: random topics in R

Writer's Bloc – my latest writing project includes R scripts

Courses in data analysis, data management and statistics.

My Publications about statistics and data analysis

Managing Data Using Excel, Cover

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