Median in R per participant for a specific variable

[LW24]

I am currently working on the data from my research. Before I can run the analysis I need to find the median for a specific variable per participant.
My data set consists of all the trials per participant and per trial there is data of that specific variable.

For example:

subjectnr trial variable X
1 1 10
1 2 8
1 3 9.5
1 4 7.5
2 1 9
2 2 12
2 3 10.5
2 4 8

How can I calculate the median for each participant?

[FJCC]

Let's say your dta are in a data frame named DF and the column names are subjectnr, trial, and variable_X. To get the mean of variable_X for each subjectnr, you can do the following:

library(dplyr)
SubjAvg <- DF |> group_by(subjectnr) |> summarize(Avg = mean(variable_X))

Note that the code requires that you have the dplyr package installed.

[LW24]

Thank you so much for your reply!
I see just now that I made a typo: i meant median in stead of mean. That is why I typed the following in R

SubjAvg <- data_voor_these_integration |> group_by(SubjNr) |> summarize(Avg = median(RT))

And this is the error that I got:

There were 50 or more warnings (use warnings() to see the first 50)

How can I fix this?

[FJCC]

Please run your code and then run

warnings()

so you can tell us what that actual warnings are.

[LW24]

Warning messages:
1: In mean.default(sort(x, partial = half + 0L:1L)[half + ... :
argument is not numeric or logical: returning NA
2: In mean.default(sort(x, partial = half + 0L:1L)[half + ... :
argument is not numeric or logical: returning NA
3: In mean.default(sort(x, partial = half + 0L:1L)[half + ... :
argument is not numeric or logical: returning NA

This is what I get

[FJCC]

It seems your RT column is not numeric. Please post the output of

dput(head(data_voor_these_integration))

Place a line with three back ticks just before and after the pasted output, like this
```
pasted output of dput() goes here
```

[LW24]

structure(list(SubjNr = c(10, 10, 10, 10, 10, 10), SubAge = c(29,
29, 29, 29, 29, 29), SubGender = c(2, 2, 2, 2, 2, 2), RefrRate = c(60,
60, 60, 60, 60, 60), StimSet = c(1, 1, 1, 1, 1, 1), Trialnr = c(1,
2, 3, 4, 5, 6), PrimeDifSame = c(1, 0, 0, 1, 0, 1), TargetDifSame = c(1,
1, 0, 1, 1, 0), CapPrime = c(0, 1, 1, 0, 0, 0), Congr = c(1,
0, 1, 1, 0, 0), PrimeLeft = c(71, 100, 103, 69, 69, 65), PrimeRight = c(103,
71, 68, 101, 97, 97), TargetLeft = c(8, 8, 8, 2, 2, 4), TargetRight = c(8,
8, 6, 2, 2, 6), RT = c("0.6559753", "0.406834", "0.4462582",
"0.6019322", "0.480397", "0.4016302"), corrResp = c(1, 1, 0,
1, 1, 0), SubjResp = c(68, 68, 68, 68, 68, 76), Acc = c(1, 1,
0, 1, 1, 1), FixDur = c("0.299999500000013", "0.300012899999274",
"0.300021699999888", "0.300019499999507", "0.300006600000415",
"0.299976199999946"), PreMaskDur = c("0.0666517999998177", "0.0666991000007329",
"0.0666160000000673", "0.0666546000002199", "0.0666656000003059",
"0.0666679000005388"), PrimeDur = c("0.0333369999998467", "0.0333193999995274",
"0.0333685999994486", "0.0333405999999741", "0.0333238999992318",
"0.033338599999297"), PostMaskDur = c("0.0666626000001997", "0.0666916999998648",
"0.0666780999999901", "0.066660899999988", "0.0666694000001371",
"0.0666556000005585"), Width = c(60, 60, 60, 60, 60, 60), Masked = c(1,
1, 1, 1, 1, 1)), row.names = c(NA, -6L), class = c("tbl_df",
"tbl", "data.frame"))

The variable "RT" is numeric, but when I write it down there is no option tab/bar where I can click on. When I wrote median or subjnr I got a list with options to choose from and click on. Does the error have something to do with that?

[nirgrahamuk]

If you see quote marks " you are not seeing a numeric, it could be a number represented as a character but not something R knows how to compute on.

Change your code to

SubjAvg <- data_voor_these_integration |> 
      group_by(SubjNr) |> 
      summarize(Avg = median(as.numeric(RT)))

[LW24]

I have changed the code to
SubjAvg <- data_voor_these_integration |>
group_by(SubjNr) |>
summarize(Avg = median(as.numeric(RT)))

But I got no output/results. I just got a new blue " > "

[nirgrahamuk]

The results have been put into SubjAvg

You can type SubjAvg into the console to see what it is