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R programming: Matrix Management

In this post lets see few basic functions to deal with matrix creation and manipulation.

# Lets assume we wish to convert existing vector v into matrix m

v <- 1:12

# Lets create matrix m from elements of v with 3 row and 4 columns

m <- matrix(v, 3, 4)

# Declare matrix with all 0 values

m <- matrix(0, 3, 4)

# values 11, 12, 13, 14, 15 in all rows

m <- matrix(11:15, 5, 4)

# Check dimensions of given matrix

dim(m)

# Total number of elements in a matrix

length(m)

# Display 4-th row and all columns

m[4, ]

# Display 3-rd column and all rows

m[ ,3]

# Select first 3 rows and 3 columns

m[1:3,1:3]

# Select all columns but only 1st, 3rd and 5th row

row <- c(1,3,5)

m[ row,]

# Add new row r1 in existing matrix m1

m <- rbind(m1, r1)

# Add new column c1 in existing matrix m1

m <- cbind(m1, c1)

# Add two matrices m1 and m2 of same dimension

m2 + m1

# Subtract two matrices m2 and m1 of same dimension

m2 - m1

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