Python
guy new to R
, so forgive the naive question.
I have an R
dataframe named metrics
with four columns:
I want to pass the level of aggregation ( day
or week
) as a variable to dcast
for aggregation.
agg_level <- c("week")
If I hard-code week
in the in the function, it aggregates data for each week correctly:
met <- dcast(metrics, week ~ city, value.var = count, fun.aggregate = sum)
week
NYC
CHI
SF
2015-10-18
1
2
3
2015-10-25
4
5
6
If I replace week
with the variable, it fails. (It aggregates data for all weeks.)
met <- dcast(metrics, agg_level ~ city, value.var = count, fun.aggregate = sum)
Output:
agg_level
NYC
CHI
SF
week
5
7
9
Based on this , metrics[[agg_level]]
extracts a column from variable, but this fails:
met <- dcast(m, [[agg_level]] ~ city, value.var = metric, fun.aggregate = sum)
Error in (function ... unexpected '[['
What is the correct way to do this?
The formula argument of dcast expects that the words passed to it are column/variable names inside of the data.frame x. It does not recognize or resolve the fact that "agg_level" is a variable. As such, you have two options:
# Option 1
# Do some text operations to make the formula based on variables.
if(this==that) {agg_level <- 'week'} else {agg_level <- 'day'}
myFormula <- sprintf("%s ~ city", agg_level)
met <- dcast(metrics, as.formula(myFormula), sum, value.var = metric)
# Option 2 - Untested
# Take advantage of dcast's alternative to the formula notation and pass a list instead.
# No idea if this will work.
met <- dcast(metrics, list(.(agg_level),.(city)), sum, value.var=metric)
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.