CODEWITHSUNDEEP
r
Aby
Aby

Reputation: 167

Subtract one row from another row in df

I have DF which looks like 

DF
Nrow  a   b    c   d
1     0.1 0.2 0.3 0.4 
2      2   3   4   5
3      7   8   9   10

I want to subtract row 1 from row 2 and row 3.

How can i do it ? Thank you for any tips.

Updates

I saw this code: within-group differences from group member, and tried it as well.

Edited my data:

newdf <- df[!is.na(S[,1]),] ## df had NA values which was interfering with analysis, so I removed them.

df <- data.frame(treatment = rep(c('','baseline', 'treatment 1', 'treatment 2'), times=372),S[c(1:258)])

A <- df %>% mutate_each(funs(. - .[treatment=="baseline"]), -treatment) %>% filter(treatment!="baseline") ##have multiple columns for which I would like to calculate row-wise change

View(A)

However, now I thought to get correct results (or absolute change, i.e. row 2 - row 1), but the values are different from what I can calculate manually. Any thoughts?

Thanks!

Answers 11.03.2016

2-y Axes Plot with calculated absolute & relative Change in R

Upvotes: 1

Views: 30836

Answers (4)

Aby
Aby

Reputation: 167

Answer 11.03.2016 #thought it might help others

This is how I finally did it:

library(dplyr) dft1= filter(df, df$time==1) dft2= filter(df, df$time==2) dft3= filter(df, df$time==3)

You might need to rename data frame or columns in accordance to your data set.

To calculate absolute change from second to first time point & third to first time point: abs1=dft2[33:290] - dft1[33:290]

abs2=dft3[33:290] - dft1[33:290]

To calculate relative change from second to first time point & third to first time point: rel1=abs1/dft1[33:290]*100

rel2=abs2/dft1[33:290]*100

Upvotes: 0

Sowmya S. Manian
Sowmya S. Manian

Reputation: 3843

The following commands would perform the subtraction of 1st row from all the rows below, and will print the result of subtraction of 1st row from rows below.

 data = data.frame(x=c(1,5,7,10),y=c(3,2,4,1.1),z=1:4)
 data
 #    x    y  z
 # 1  1  3.0  1
 # 2  5  2.0  2
 # 3  7  4.0  3
 # 4 10  1.1  4

 for(i in 2:nrow(data)){
 result = data[i,] - data[1,]
 print (result)
 }

 #     x   y  z    
 # 2   4  -1  1     <--- 2nd row minus 1st row

 #     x   y  z
 # 3   6   1  2     <--- 3rd row minus 1st row

 #     x   y  z
 # 4   9 -1.9 3     <--- 4th row minus 1st row

Hope this helped. You can use the same commands for any number of rows in your data.

Upvotes: 0

cory
cory

Reputation: 6669

Use indexes to look at rows...

df <- read.table(textConnection("Nrow  a   b    c   d
1     0.1 0.2 0.3 0.4 
2      2   3   4   5
3      7   8   9   10"), stringsAsFactors=FALSE, header=TRUE)

df[1, ] - df[2, ]
# or assign the result to a new row...
df <- rbind(df, df[1, ] - df[2, ])

Upvotes: 0

akrun
akrun

Reputation: 887961

If we need to subtract a single row from multiple rows, we can rep the the single row to make the dimension as that of the subset of dataset with multiple rows and then do the subtraction.

DF[2:3, -1]- DF[rep(1,2),-1]
#   a   b   c   d
#2 1.9 2.8 3.7 4.6
#3 6.9 7.8 8.7 9.6

data

DF <- structure(list(Nrow = 1:3, a = c(0.1, 2, 7), b = c(0.2, 3, 8), 
c = c(0.3, 4, 9), d = c(0.4, 5, 10)), .Names = c("Nrow", 
"a", "b", "c", "d"), class = "data.frame",
 row.names = c(NA, -3L))

Upvotes: 2

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