Hi,
I have the following dataframe and I am wondering how to subtract the value in the first row to values in the same column.
I would also be interested to know how to subtract any column or value to other rows.
data.frame(
stringsAsFactors = FALSE,
Sample = c("Blank", "ProtA", "ProtB", "ProtC"),
Activity = c(0.033, 0.245, 0.31, 0.105)
)
#> Sample Activity
#> 1 Blank 0.033
#> 2 ProtA 0.245
#> 3 ProtB 0.310
#> 4 ProtC 0.105
Thank you in advance.
Here are two methods. In the first the values are changed in the original column and in the second, which I prefer, a new column is made with the adjusted values.
DF <- data.frame(
stringsAsFactors = FALSE,
Sample = c("Blank", "ProtA", "ProtB", "ProtC"),
Activity = c(0.033, 0.245, 0.31, 0.105)
)
DF
#> Sample Activity
#> 1 Blank 0.033
#> 2 ProtA 0.245
#> 3 ProtB 0.310
#> 4 ProtC 0.105
DF$Activity <- DF$Activity - DF[1,2]
DF
#> Sample Activity
#> 1 Blank 0.000
#> 2 ProtA 0.212
#> 3 ProtB 0.277
#> 4 ProtC 0.072
#Make a new column
DF <- data.frame(
stringsAsFactors = FALSE,
Sample = c("Blank", "ProtA", "ProtB", "ProtC"),
Activity = c(0.033, 0.245, 0.31, 0.105)
)
DF
#> Sample Activity
#> 1 Blank 0.033
#> 2 ProtA 0.245
#> 3 ProtB 0.310
#> 4 ProtC 0.105
DF$ActivityAdj <- DF$Activity - DF[1,2]
DF
#> Sample Activity ActivityAdj
#> 1 Blank 0.033 0.000
#> 2 ProtA 0.245 0.212
#> 3 ProtB 0.310 0.277
#> 4 ProtC 0.105 0.072
Created on 2020-05-22 by the reprex package (v0.3.0)
Thank you for your fast response @FJCC.
Is there a way to also delete the row NULL directly or is it something that I can only do later, for example by selecting row 2 to 4 to create a new dataframe?
Thanks again!
The easiest method is to select rows 2 to 4, as you suggest.
I tried with a more complex example, more representative of my data but I do not really understand why it does not work. It always makes result equal to zero.
Is it because I group my samples in order to determine the mean for each group?
> Rstudio_Examples <- read_excel("Desktop/Rstudio-Examples.xlsx")
> View(Rstudio_Examples)
> Enzyme <- Rstudio_Examples
> head(Enzyme, 8)[, c('Sample', '24H')]
# A tibble: 8 x 2
Sample `24H`
<chr> <dbl>
1 Blank 0.033
2 Blank 0.035
3 ProtA 0.201
4 ProtA 0.188
5 ProtB 0.345
6 ProtB 0.321
7 ProtC 0.245
8 ProtC 0.222
> datapasta::df_paste(head(Enzyme, 8)[, c('Sample', '24H')])
> data.frame(
+ stringsAsFactors = FALSE,
+ check.names = FALSE,
+ Sample = c("Blank","Blank","ProtA",
+ "ProtA","ProtB","ProtB","ProtC","ProtC"),
+ `24H` = c(0.033, 0.035, 0.201, 0.188, 0.345, 0.321, 0.245, 0.222)
+ )
Sample 24H
1 Blank 0.033
2 Blank 0.035
3 ProtA 0.201
4 ProtA 0.188
5 ProtB 0.345
6 ProtB 0.321
7 ProtC 0.245
8 ProtC 0.222
> Enzymes_24H <- Enzyme %>% group_by(Sample) %>% summarize(Mean = mean(`24H`))
> View(Enzymes_24H)
> Enzymes_24H <- Enzymes_24H %>% rename("24H" = "Mean")
> View(Enzymes_24H)
> Enzymes_24H$ActivityAdj <- Enzymes_24H$"24H" - Enzymes_24H[1,2]
> View(Enzymes_24H)
> head(Enzymes_24H, 4)[, c('Sample', '24H', 'ActivityAdj')]
# A tibble: 4 x 3
Sample `24H` ActivityAdj$`24H`
<chr> <dbl> <dbl>
1 Blank 0.034 0
2 ProtA 0.194 0
3 ProtB 0.333 0
4 ProtC 0.233 0
>
Thank you in advance.
Does this help?
library(dplyr)
#>
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#>
#> filter, lag
#> The following objects are masked from 'package:base':
#>
#> intersect, setdiff, setequal, union
Enzyme <- tibble(Sample = c("Blank", "Blank", "ProtA", "ProtA", "ProtB", "ProtB", "ProtC", "ProtC"),
`24H` = c(0.033, 0.035, 0.201, 0.188, 0.345, 0.321, 0.245, 0.222))
Enzyme %>%
group_by(Sample) %>%
summarize(Mean = mean(`24H`)) %>%
rename("24H" = "Mean") %>%
mutate(ActivityAdj = `24H` - first(x = `24H`))
#> # A tibble: 4 x 3
#> Sample `24H` ActivityAdj
#> <chr> <dbl> <dbl>
#> 1 Blank 0.034 0
#> 2 ProtA 0.194 0.160
#> 3 ProtB 0.333 0.299
#> 4 ProtC 0.233 0.199
As to why you failed, when you extract an element from a data.frame, it's a vector. But if you extract from a tibble, it's a tibble itself, of one variable and one observation. Subtraction of a tibble of suzh shape from a vector returns the result for first element of vector only, and then it gets replicated to match the length. That's why you are getting all zeros.
Now I think this is the reason just by checking a few combinations. These, especiallly extracting one element still being a tibble, seems odd to me. But there may be a documentation somewhere which I missed.
Hope this helps.
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