R help - Jun 2009 - simple loop

Hi everyone!

I have this dataframe:

firm<-c(rep(1,4),rep(2,4),rep(3,4),rep(4,4),rep(5,4),rep(6,4))
year<-c(rep(2000:2003,6))
industry<-c(rep(10,4),rep(20,4),rep(30,4),rep(10,4),rep(20,4),rep(30,4))
X1<-c(10,14,18,16,20,45,23,54,24,67,98,58,16,32,57,12,54,0,0,22,11,3,5,6)
data<-data.frame(firm, industry,year,X1)
data

I need a loop that calculates the mean of X1 by year and 
by industry and I need this values in a dataframe or a 
matrix.
I have done:

means<-matrix(nrow=3,ncol=4)

for ( i in unique(data$industry))
  for (j in 
data$year){means[i,j]<-mean(data$X1,na.rm=TRUE)}

But it doesn?t work. Could anyone help me?

Cec?lia Carmo

Dear Cecilia,
Here is one way:

 with(<yourdata>, tapply(X1, list(year, industry), mean))

Also, take a look at ?ave and its examples.

HTH,

Jorge


On Sun, Jun 28, 2009 at 12:39 PM, Cecilia Carmo <cecilia.carmo@ua.pt>
wrote:
> Hi everyone!
>
> I have this dataframe:
>
> firm<-c(rep(1,4),rep(2,4),rep(3,4),rep(4,4),rep(5,4),rep(6,4))
> year<-c(rep(2000:2003,6))
> industry<-c(rep(10,4),rep(20,4),rep(30,4),rep(10,4),rep(20,4),rep(30,4))
>
X1<-c(10,14,18,16,20,45,23,54,24,67,98,58,16,32,57,12,54,0,0,22,11,3,5,6)
> data<-data.frame(firm, industry,year,X1)
> data
>
> I need a loop that calculates the mean of X1 by year and by industry and I
> need this values in a dataframe or a matrix.
> I have done:
>
> means<-matrix(nrow=3,ncol=4)
>
> for ( i in unique(data$industry))
>  for (j in data$year){means[i,j]<-mean(data$X1,na.rm=TRUE)}
>
> But it doesn´t work. Could anyone help me?
>
> Cecília Carmo
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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Hi Cecilia,

Trying it your way there where three reasons for errors, I fixed them in the
following code:


means<-matrix(nrow=3,ncol=4)

counter.i <- 0
counter.j <- 0

for (i in levels(factor(data$industry)))
{
counter.i <- counter.i + 1
 for (j in levels(factor(data$year)))
{
counter.j <- counter.j + 1
 means[counter.i,counter.j]<- mean(data$X1 [data$industry == i &
data$year
== j]  ,na.rm=TRUE)
}
 counter.j <- 0
}

means



Also consider ddply in the plyr package (although that's an over kill if
your only having two loops)

Or Jorge solution.

Cheers,
Tal G





On Sun, Jun 28, 2009 at 7:39 PM, Cecilia Carmo <cecilia.carmo@ua.pt>
wrote:
> for ( i in unique(data$industry))
>  for (j in data$year){means[i,j]<-mean(data$X1,na.rm=TRUE)}
>


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