[PS] How to manipulate data according to groups ?
Look at ?tapply, based on your description, it is what you want. Ben -----Original Message----- From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Ng Stanley Sent: Thursday, March 13, 2008 9:25 AM To: r-help Subject: [PS] [R] How to manipulate data according to groups ? Hi, I have a two columns data, the first column are values, and second column are the groups. For this example, there are 3 groups 1,2,3. How can I manipulate the values in the first column according to groups, say I would like to find mean, sum, and standard deviation for the different groups ? How do I plot data according to groups ?
t <- matrix(c(rnorm(10), 1,1,2,2,1,3,3,3,3,2), ncol=2)
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