Goal

The goal of this tutorial is to know how to replace an specific value in different positions of a dataframe for another value using a for loop.

Data creation

To deploy the function a dataframe should be created.

## Dataframe generation from vectors
S001 <- c(100,-20, -30, -76, 100, 100, 0, -5, 100, -102, 100, 100, 100, -89, 100)
S002 <- c(100,100, -90, -44, 100, -10, 100, 100, 100, 100, -80, -6, 100, -67, 100)
S003 <- c( 0, -9, 100, -65, 100,100,-103, -30, -76, 100, 100, 100, 100, -77, 100)
S004 <- c( 100, -99, 100, 100, 100,-100,-103, 100, -76, -15, 100, 100, -79, 100, 100)

My_DataSet <- data.frame(S001,S002,S003,S004) 

My_DataSet

##    S001 S002 S003 S004
## 1   100  100    0  100
## 2   -20  100   -9  -99
## 3   -30  -90  100  100
## 4   -76  -44  -65  100
## 5   100  100  100  100
## 6   100  -10  100 -100
## 7     0  100 -103 -103
## 8    -5  100  -30  100
## 9   100  100  -76  -76
## 10 -102  100  100  -15
## 11  100  -80  100  100
## 12  100   -6  100  100
## 13  100  100  100  -79
## 14  -89  -67  -77  100
## 15  100  100  100  100

Find specific value and replace

The aim of this section is evaluate all the positions of a dataframe compare with the value that we want to replace and replace it with the new one.

## Variables creation of the value to be replaced and new one

Old_value <- 100 
# This could also be a multiple values subtitution like Old_value <- c(100, 150)

New_value <- 200

## Loops to evaluate step by step the all of the positions of dataframe  
## and assign the new valuein case the condition is fulfilled

for (i in seq_along(My_DataSet)) {
    My_DataSet[[i]][My_DataSet[[i]] %in% Old_value] <- New_value
}

My_DataSet

##    S001 S002 S003 S004
## 1   200  200    0  200
## 2   -20  200   -9  -99
## 3   -30  -90  200  200
## 4   -76  -44  -65  200
## 5   200  200  200  200
## 6   200  -10  200 -100
## 7     0  200 -103 -103
## 8    -5  200  -30  200
## 9   200  200  -76  -76
## 10 -102  200  200  -15
## 11  200  -80  200  200
## 12  200   -6  200  200
## 13  200  200  200  -79
## 14  -89  -67  -77  200
## 15  200  200  200  200

Conclusions

In this tutorial we learned how to replace an specific value for another one.