CODEWITHSUNDEEP
r
shawin karim
shawin karim

Reputation: 81

Looping over a data frame in R

I have a data frame and I'm trying to calculate median for each group separately. When I separate the data frame in two groups and calculate the median for each one, I am getting an NA result.

The data is :

    x1  x2  x3  x4  x5  x6  x7  y1  y2  y3  y4  y5  y6  y7  y8
9.488404158 9.470895414 9.282433728 9.366707445 9.955383045 9.640816474   9.606262272   9.329651027 9.434541611 9.473922432 9.311412966 9.3154885   9.434977488 9.470895414 9.764258059
8.630629966 8.55831075  8.788391003 8.576231135 8.671587906 8.842979993 8.861958856 8.58330436  8.603596508 8.570129609 8.59798922  8.572686772 8.679751791 8.663950953 8.432875347
9.354748885 9.367668838 9.259952558 9.421538213 9.554635162 9.603744578 9.452197983 9.284228877 9.404607878 9.317737979 9.343115301 9.310644266 9.27227486  9.360337823 9.44706281
9.944863964 9.950427516 10.19101759 10.07350804 10.03269879 10.1307908  10.03487287 9.74609383  9.886379007 9.775472567 10.036596   9.544738458 9.699611598 9.911962567 9.625804277

Code:

  rowN <- nrow(AT1)
  MD1<-vector(length=rowN)
  MD2<-vector(length=rowN)

   MD1[1:rowN]<-NA
   MD2[1:rowN]<-NA


 x<- AT1[,c(2,3,4,5,6,7,8) ]
  write.csv(x,"x.csv",row.names=TRUE)
  x<-as.matrix(x)
  for(i in 2:rowN) { 
  MD1[i]=median(x[i,])
  }
 write.csv(MD1,"MD1.csv",row.names=TRUE)

  y<- AT1[,c(9,10,11,12,13,14,15,16)]
  write.csv(y,"y.csv",row.names=TRUE)
  y<-as.matrix(y)
  for(j in 2:rowN) {
  MD2[j]=median(y[j,])
  }
  write.csv(MD2,"MD2.csv",row.names=TRUE)

Upvotes: 0

Views: 94

Answers (1)

akrun
akrun

Reputation: 886938

It would have been better to show a reproducible example. Based on the loop code, it seems to me that the OP want to get the median of each row. Assuming that the median is calculated for columns 2:8 and for 9:16 separately, we convert the 'data.frame' to 'matrix' (as.matrix) and use rowMedians from library(matrixStats).

x1 <- as.matrix(AT1[2:8 ])
x2 <- as.matrix(AT1[9:16])

library(matrixStats)
rowMedians(x1, na.rm=TRUE)
#[1] -0.09411013 -0.08554095  0.11953107 -0.26869311  0.33224445

rowMedians(x2, na.rm=TRUE)
#[1]  0.10557881 -0.74135403 -0.05876725  0.69230776 -0.21402339

data

set.seed(24)
m1 <- matrix(rnorm(5*15), ncol=15)
AT1 <- data.frame(col1= LETTERS[1:5], m1)

Upvotes: 3

Related Questions