R: how to average every 7th row

Question

I want to take the average of each column (except the date) after every seven rows. I tried the approach below, but I was getting incorrect values. This method also seems really long. Is there a way to shorten it?

bankamerica = read.csv('https://raw.githubusercontent.com/bandcar/Examples/main/bankamerica.csv')

library(tidyverse)
GroupLabels <- 0:(nrow(bankamerica) - 1)%/% 7
bankamerica$Group <- GroupLabels

Avgs <- bankamerica %>% 
  group_by(bankamerica$Group) %>% 
  summarize(Avg = mean(bankamerica$tr))

EDITED: Just realized this code provides the incorrect values

Answer 1

I think you're on the right path.

bankamerica %>%
  mutate(group = cumsum(row_number() %% 7 == 1)) %>%
  group_by(group) %>%
  summarise(caldate = first(caldate), across(-caldate, mean)) %>%
  select(-group)
## A tibble: 144 × 3
#   caldate    tr   var
#   <chr>   <dbl> <dbl>
# 1 1/2/01  28.9  -50.6
# 2 1/11/01 23.6  -45.4
# 3 1/23/01 20.9  -45  
# 4 2/1/01  17.4  -48  
# 5 2/12/01 14.4  -48  
# 6 2/21/01 17    -48.9
# 7 3/2/01  19.1  -56  
# 8 3/13/01 19.4  -56.9
# 9 3/22/01 23.3  -55.7
#10 4/2/01   7.71 -58.3
    

This averages every 7 rows not every 7 days, because there are missing days in the data.