For 循环以获取跨多个向量的索引平均值（时间序列平均值图）

Question

I am currently developing my pipeline in R for data processing/analysis.

My data is in a long format (sample rate = 1000Hz). Throughout the dataframe I have added a trialNum variable for each trial, but I am having issues reshaping my data to wide.

What I am trying to do, and I think should be possible with a for loop or two... Is to get the average value of x at index 1:100, based on the trialNum.

Here is a simple version...

Pupil Size	TrialNum
500	1
502	1
504	1
506	1
508	1
507	2
508	2
510	2
511	2
512	2
513	3
515	3
514	3
512	3
515	3

So stated simply... I would get the first index of Pupil size for each TrialNum, and average together, and add to a new variable (average_pupil_size).

In this example, each trial has 5 inputs, so I would end up with a variable output of length = 5...

average_size <- c(507, 508, 509, 510, 512)

I could then plot this signal for all my trials... I hope I have explained myself clearly... Apologies for the chaos that is my mind.

Does anyone know how to do this? It is a bit beyond me.

Thanks in advance!

Answer 1

We could add an index within each TrialNum using row_number() , and then group-summarize within those.

library(dplyr)
df %>%
  group_by(TrialNum) %>%
  mutate(index = row_number()) %>%
  group_by(index) %>%
  summarize(avg = mean(Pupil.Size))

Result

# A tibble: 5 × 2
  index   avg
  <int> <dbl>
1     1  507.
2     2  508.
3     3  509.
4     4  510.
5     5  512.

Answer 2

in base R, if the data has same length for each trial, eg in this case 5, we can do:

rowMeans(unstack(df))

[1] 506.6667 508.3333 509.3333 509.6667 511.6667