Setting condition for max within mutate function of dplyr

Question

I am looking to determine the max score within a data set but only when looking the group population is above a certain threshold, in this case above 20. sample data:

Race = c("African American", "Asian", "Hispanic", "White")
Population = c(28, 11, 31, 64)
Average_Score = c(65, 82, 49, 75)
df = data.frame(Race, Population, Average_Score)

    Race            Population Average_Score
1 African American      28           65
2 Asian                 11           82
3 Hispanic              31           49
4 White                 64           75

What I would like to do is something like:

df %>% mutate(reference=max(Average_Score)) where Population > 20

however, I need to add a condition so that it only pulls the max(Average_Score) where Population is greater than 20. In this case, instead of returning Average_Score of 82 (because the Asian population is less than 20) it would return Average_Score of 75 (because the highest Average_Score of any group with Population greater than 20 is the Average_Score that coincides with White)

Any help would be greatly appreciated.

You need max(Average_Score[Population > 20])

akrun
– akrun

2019-01-28 18:44:31 +00:00
Commented Jan 28, 2019 at 18:44 — akrun
– akrun, Commented Jan 28, 2019 at 18:44
thanks! that worked great!

Tyler
– Tyler

2019-01-29 23:03:45 +00:00
Commented Jan 29, 2019 at 23:03 — Tyler
– Tyler, Commented Jan 29, 2019 at 23:03

Tyler · Accepted Answer · 2019-01-29 23:06:10Z

1

I used akrun's suggestion:

max(Average_Score[Population > 20])

but nycrefugee's also worked:

df %>% 
  filter(Population > 20) %>%
  filter(Average_Score == max(Average_Score))

answered Jan 29, 2019 at 23:06

Tyler

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Comments

DeduciveR · Accepted Answer · 2019-01-28 22:18:37Z

0

a dplyr solution that might offer some more flexibility.

df %>% 
  filter(Population > 20) %>%
  filter(Average_Score == max(Average_Score))

   Race Population Average_Score
1 White         64            75

answered Jan 28, 2019 at 22:18

DeduciveR

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1 Comment

Tyler Over a year ago

Thanks! The way that the code was set up, I ended up using the code suggested by akrun above: max(Average_Score[Population > 20])

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