Using tapply to sum by category

Good use of R’s tapply function to summary data ..

## read a csv file into a table called x – the first row contains column names

x<-read.table("2014-tax.csv",sep=",",header=T)

## In my instance column names are Item,Amount,Cat,Month,Who
## split out by Who

bob<-x[x$Who == "bob",] jane<-x[x$Who == "jane",]

## Spin around each row (obs) and sum the Amount

print(tapplybob$Amount,bob$Cat,sum))

## Typical output for bob #

#  books  equipment licences stationery  supplies    telephone

# 303.00 694.27 132.00 345.50 96.00 30.00
#


# Then for jane

print(tapply(jane$Amount,jane$Cat,sum)) 

# books equipment licences stationery supplies telephone

# 163.0 583.0 348.0 678.4 11543.0 NA
#
#

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