使用 cut 然后在包 plyr 中使用 ddply ：

 > df $ xrange<  -  cut（df $ x，breaks = seq（0，100，10））

库（plyr）
 ddply（df，。（xrange） mean_y = mean（y））
 xrange mean_y 
 1（0,10）490.7571 
 2（10,20）462.6347 
 3（20,30）507.5614 
 4（30,40）482.6004 
 5（40,50] 510.3081 
 6（50,60）480.7927 
 7（60,70）507.8944 
 8（70,80] 458.4668 
 9（80,90] 501.9672 
 10（90,100）493.4844 
 

If I have a series of observations with two variables X and Y, how can I get the average value of Y based on ranges of variable X?

So for example, with some data like:

df = data.frame(x=runif(50,1,100),y=runif(50,300,700))

How could I get the answer to "When X is 1-10 the average of y 332.4, when X is 11-20 the average of y is 632.3, etc...."

Cut your x using cut and then use ddply in package plyr:

> df$xrange <- cut(df$x, breaks=seq(0, 100, 10))

library(plyr)
ddply(df, .(xrange), summarize, mean_y=mean(y))
     xrange   mean_y
1    (0,10] 490.7571
2   (10,20] 462.6347
3   (20,30] 507.5614
4   (30,40] 482.6004
5   (40,50] 510.3081
6   (50,60] 480.7927
7   (60,70] 507.8944
8   (70,80] 458.4668
9   (80,90] 501.9672
10 (90,100] 493.4844