R：一次汇总几个列

Question

I am new to R and this is the first time I use stackoverflow so excuse me if I ask for something obvious or my question is not clear enough.

I am working with the following data set

dim(storm)
[1] 883602     39


    names(storm)
   [1] "STATE__"    "BGN_DATE"   "BGN_TIME"   "TIME_ZONE"  "COUNTY"
   [6] "COUNTYNAME" "STATE"      "EVTYPE"     "BGN_RANGE"  "BGN_AZI"
   [11] "BGN_LOCATI" "END_DATE"   "END_TIME"   "COUNTY_END" "COUNTYENDN"
   [16] "END_RANGE"  "END_AZI"    "END_LOCATI" "LENGTH"     "WIDTH"
   [21] "F"          "MAG"        "FATALITIES" "INJURIES"   "PROPDMG"
   [26] "PROPDMGEXP" "CROPDMG"    "CROPDMGEXP" "WFO"        "STATEOFFIC"
   [31] "ZONENAMES"  "LATITUDE"   "LONGITUDE"  "LATITUDE_E" "LONGITUDE_"
   [36] "REMARKS"    "REFNUM"     "PROPTOTAL"  "CROPTOTAL"

I am interested to use EVTYPE (a factor variable) to aggregate 4 other numerical variables ( PROPTOTAL, CROPTOTAL, FATALITIES, INJURIES )

The factor variable as 950 levels:

length(unique(storm$EVTYPE))
[1] 950


class(storm$EVTYPE)
[1] "factor"

So I would expect an aggregated data frame with 950 observations and 5 variables when I run the following command:

    storm_tidy<-
aggregate(cbind(PROPTOTAL,CROPTOTAL,FATALITIES,INJURIES)~EVTYPE,FUN=sum,data=storm)

However I get only 155 rows

dim(storm_tidy)
[1] 155   5

I am using the aggregate with several columns following the help page of the function (use cbind):

Formulas, one ~ one, one ~ many, many ~ one , and many ~ many:
aggregate(weight ~ feed, data = chickwts, mean) aggregate(breaks ~ wool + tension, data = warpbreaks, mean) **aggregate(cbind(Ozone, Temp) ~ Month, data = airquality, mean)** aggregate(cbind(ncases, ncontrols) ~ alcgp + tobgp, data = esoph, sum)

I am loosing information at some point:

sum(storm$PROPTOTAL)
[1] 424769204805

sum(storm_tidy$PROPTOTAL)
[1] 228366211339

However, if I aggregate column by column it seems to work fine:

storm_tidy <- aggregate(PROPTOTAL~EVTYPE,FUN = sum, data = storm)
dim(storm_tidy)
[1] 950   2





sum(storm_tidy$PROPTOTAL)
[1] 424769204805

What am I missing? What am I doing wrong?

Thanks.

Answer 1

This could be a case where there are missing values in some of the columns and the entire row is deleted based on the default option na.action= na.omit in the aggregate . I would try with na.action=NULL

aggregate(cbind(PROPTOTAL,CROPTOTAL,FATALITIES,INJURIES)~EVTYPE,
            FUN=sum, na.rm=TRUE, data=storm, na.action=NULL)

Or we can use summarise_each from dplyr after grouping by 'EVTYPE`

library(dplyr)
storm %>% 
   group_by(EVTYPE) %>% 
   summarise_each(funs(sum=sum(., na.rm=TRUE)), 
                 PROPTOTAL,CROPTOTAL,FATALITIES,INJURIES)