CODEWITHSUNDEEP
rmatrix
jthemapper
jthemapper

Reputation: 23

Merge and replace values from overlapping matrices

I have two overlapping matrices with some shared columns and rows:

m.1 = matrix(c(NA,NA,1,NA,NA,NA,1,1,1,NA,1,1,1,1,1,NA,1,1,1,NA,NA,NA,1,NA,NA), ncol=5)
colnames(m.1)  <- c("-2","-1","0","1","2")
rownames(m.1)  <- c("-2","-1","0","1","2")

##    -2 -1 0  1  2
## -2 NA NA 1 NA NA
## -1 NA  1 1  1 NA
##  0  1  1 1  1  1
##  1 NA  1 1  1 NA
##  2 NA NA 1 NA NA

m.2 = matrix(c(NA,2,NA,2,2,2,NA,2,NA), ncol=3)
colnames(m.2)  <- c("-1","0","1")
rownames(m.2)  <- c("-1","0","1")

##    -1 0  1
## -1 NA 2 NA
##  0  2 2  2
##  1 NA 2 NA

Now I want to pass the maximum value in each column from m.1 and m.2 to a new matrix m.max, which should look like this:

##    -2 -1 0  1  2
## -2 NA NA 1 NA NA
## -1 NA  1 2  1 NA
##  0  1  2 2  2  1
##  1 NA  1 2  1 NA
##  2 NA NA 1 NA NA

Based on previous threads, I have meddled with merge(), replace() and match() but cannot get the desired result at all, e.g.

m.max<- merge(m.1,m.2, by = "row.names", all=TRUE, sort = TRUE)

##   Row.names -2 -1.x 0.x 1.x  2 -1.y 0.y 1.y
## 1        -1 NA    1   1   1 NA   NA   2  NA
## 2        -2 NA   NA   1  NA NA   NA  NA  NA
## 3         0  1    1   1   1  1    2   2   2
## 4         1 NA    1   1   1 NA   NA   2  NA
## 5         2 NA   NA   1  NA NA   NA  NA  NA

Please help! Am I completely on the wrong track? Does this operation require a different kind of object than matrix? For example, I also tried to convert the matrices into raster objects and do cell statistics, but ran into problems because of the unequal dimensions of m.1 and m.2.

Importantly, the answer should also work for much larger objects, or whether I want to calculate the maximum, minimum or sum.

Upvotes: 2

Views: 549

Answers (1)

nicola
nicola

Reputation: 24490

You can use pmax:

#we create a new matrix as big as m.1 with the values of m.2 in it
mres<-array(NA,dim(m.1),dimnames(m.1))
mres[rownames(m.2),colnames(m.2)]<-m.2
#Then we use pmax
pmax(m.1,mres,na.rm=TRUE)
#   -2 -1 0  1  2
#-2 NA NA 1 NA NA
#-1 NA  1 2  1 NA
#0   1  2 2  2  1
#1  NA  1 2  1 NA
#2  NA NA 1 NA NA

Upvotes: 3

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