Using for loop for iterations

The most convenient way to perform iterative operation in R is the use of a for loop. Suppose you are given a dataset with five variables representing five different diseases for 10 people. All your variables are binary. Your task is to calculate the frequency of each variable as well as the cross-frequency of all pair-wise variables. Using a for loop, you can easily complete this task. In this recipe, you will implement a for loop to calculate the disease frequency and the frequency of all pair-wise variables.

Getting ready

Let’s consider you are given the following dataset mat:

    set.seed(1234)
    mat<-matrix(sample(c(0,1),50,replace = T),nrow = 10,ncol=5)
    rownames(mat) <- paste("patient", paste(1:10),sep="")
    colnames(mat) <- c("diabetes", "hypertension", "asthma",  
    "jointPain", "fever")
    > mat
              diabetes hypertension asthma jointPain fever
    patient1         0            1      0         0     1
    patient2     ...