cbind: Merge according to the column, that is, superimpose all columns. The matrix of m column and the matrix of n columns cbind() finally become m+n columns. The prerequisite for merging: the number of rows of matrices a and c in cbind(a, c) must match the number of rows of matrices a and c in cbind(a, c)
rbind: Merge according to rows, that is, superposition of rows. The matrix of m rows and n rows of matrix rbind() finally becomes m+n rows. The prerequisite for merging: the number of columns of matrices a and c in rbind(a, c) must match the number of columns of matrices a and c in rbind(a, c)
> a <- matrix(1:12, 3, 4) > print(a) [,1] [,2] [,3] [,4] [1,] 1 4 7 10 [2,] 2 5 8 11 [3,] 3 6 9 12 > > b <- matrix(-1:-12, 3, 4) > print(b) [,1] [,2] [,3] [,4] [1,] -1 -4 -7 -10 [2,] -2 -5 -8 -11 [3,] -3 -6 -9 -12 > > x=cbind(a,b) > print(x) [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [1,] 1 4 7 10 -1 -4 -7 -10 [2,] 2 5 8 11 -2 -5 -8 -11 [3,] 3 6 9 12 -3 -6 -9 -12 > > y=rbind(a,b) > print(y) [,1] [,2] [,3] [,4] [1,] 1 4 7 10 [2,] 2 5 8 11 [3,] 3 6 9 12 [4,] -1 -4 -7 -10 [5,] -2 -5 -8 -11 [6,] -3 -6 -9 -12 > > > c <- matrix(-1:-20, 4, 5) > print(c) [,1] [,2] [,3] [,4] [,5] [1,] -1 -5 -9 -13 -17 [2,] -2 -6 -10 -14 -18 [3,] -3 -7 -11 -15 -19 [4,] -4 -8 -12 -16 -20 > > x2=cbind(a,c) Error in cbind(a, c) : The number of rows of the matrix must match(Seearg2) > print(x2) [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [1,] 1 4 7 10 -1 -4 -7 -10 -13 [2,] 2 5 8 11 -2 -5 -8 -11 -14 [3,] 3 6 9 12 -3 -6 -9 -12 -15 > > y2=rbind(a,c) Error in rbind(a, c) : The number of columns of the matrix must match(Seearg2) > print(y2) Error in print(y2) : The object cannot be found'y2' >
merge function
Two data frames have the same time or observations, but the columns are not the same. The way to deal with it is to use
merge(x, y, = , = , all = ) function.
#merge/mergeID<-c(1,2,3,4) name<-c(“A”,”B”,”C”,”D”) score<-c(60,70,80,90) student1<-(ID,name) student2<-(ID,score) total_student1<-merge(student1,student2,by=”ID”) total_student1
When we need to merge different types of variables derived from the same observation object, cbind is used, that is, merging column.
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