This tutorial explains how to aggregate or summarize data.

**Create a sample data**set.seed(1)

data <- data.frame(X = paste("s", sample(1:3, 15, replace = TRUE), sep = ""),Y = ceiling(rnorm(15)), Z = rnorm(15), A = rnorm(15), B = rnorm(15))

Sample Data |

**Calculate Mean of Z by grouping variable X**

dat1 = aggregate(Z ~ X, data=data, FUN=mean)

**Calculate Mean of Z by 2 grouping variables**

dat2 = aggregate(Z~ X + Y, data=data, FUN=mean)

**Calculate Mean of Y and Z by grouping variable X**

dat3 = aggregate(cbind(Y,Z)~X, data=data, FUN=mean)

**Calculate Mean of all the variable by grouping variable X**

dat4 = aggregate(.~X, data=data, FUN=mean)

**Concatenate Text Based on Criteria**

testDF <- data.frame(v1 = c(1,3,5,7,8,3,5,NA,4,5,7,9),

v2 = c(11,33,55,77,88,33,55,25,44,55,77,99) )

aggregate(v2 ~ v1, data = testDF, FUN=paste, sep=",")

Hi, btw what does ceiling in rnorm (ceiling(rnorm(15)) means?

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