CODEWITHSUNDEEP
rmax
Pinus2Quercus
Pinus2Quercus

Reputation: 91

Creating a summary table of maximum values

I have a matrix of daily data of average flow and want to make a summary matrix that shows the maximum peak flow. Here's a little sample of what my data looks like:

x<-c(5,10,15,20,25,30,35,40,45,50,55,60,65,70,75,80,85,90,95,100)
flow<-matrix(c(c(rep(1990,365),rep(1991,365),rep(1992,365)),sample(x,(365*3), replace=TRUE)),nrow=(365*3), ncol=2)

I'd like the summary matrix to be formatted with the year in column 1 and the peak flow event from that year in column 2. Here's an example of how I would like the summary matrix formatted.

summary=matrix(, ncol=2, nrow=3)
summary[,1]=c(1990,1991,1992)

Upvotes: 1

Views: 81

Answers (2)

untitled
untitled

Reputation: 152

And the dplyr family of functions (building on @Bryans work):

DF <- as.data.frame(flow)
names(DF) <- c("year", "flow")
group_by(DF, year) %>% summarize(flow = max(flow))

Gives:

Source: local data frame [3 x 2]

  year flow
1 1990  100
2 1991  100
3 1992  100

Upvotes: 1

Bryan Hanson
Bryan Hanson

Reputation: 6213

This should be close:

DF <- as.data.frame(flow)
names(DF) <- c("year", "flow")
DF$year <- as.factor(DF$year)
res <- aggregate(flow ~ year, data = DF, FUN = max)

And gives:

  year flow
1 1990  100
2 1991  100
3 1992  100

in the form of a data frame.

Upvotes: 5

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