# [R] set dataframe field value from lookup table

Jon Erik Ween jween at klaru-baycrest.on.ca
Thu Dec 9 15:34:29 CET 2010

```Hi

This is (hopefully) a bit more cogent phrasing of a previous post. I'm
trying to compute a z-score to rows in a large dataframe based on values in
another dataframe. Here's the script (that does not work). 2 questons,

1) Anyone know of a more elegant way to calculate the "rounded" age value
than the nested ifelse's I've used?

2) how to reference the lookup table based on computed indices?

Thanks

Jon

# Define tables
DSTzlook <-
df<-stroke

# Compute rounded age.
df\$Agetmp
<-ifelse(df\$Age>=89,89,ifelse(df\$Age>=84,84,ifelse(df\$Age>=79,79,ifelse(df\$Age>=74,74,ifelse(df\$Age>=69,69,ifelse(df\$Age>=64,64,ifelse(df\$Age>=54,54,ifelse(df\$Age>=44,44,ifelse(df\$Age>=34,34,ifelse(df\$Age>=29,29,ifelse(df\$Age>=24,24,ifelse(df\$Age>=19,19,17))))))))))))

# Reference the lookup table based on computed indices
df\$DSTz
<-DSTzlook[which(DSTzlook[,1]==df\$Agetmp),which(DSTzlook[1,]==df\$DSF+df\$DSB)]

# Cleanup
#rm(df)
#df\$Agetmp<-NULL
--
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```