cbind converting factor to numeric

问题

Not sure why this is happening. I have a dataframe df2 with the variables below:

          EVTYPE TOTAL_FATALITIES TOTAL_INJURIES
          (fctr)            (dbl)          (dbl)
1        TORNADO             5633          91346
2 EXCESSIVE HEAT             1903           6525
3    FLASH FLOOD              978           1777
4           HEAT              937           2100
5      LIGHTNING              816           5230
6      TSTM WIND              504           6957

    > df2$TOTAL_FATALITIES

 [1] 5633 1903  978  937  816  504  470  368  248  224  206  204  172  160  133  127  103  101  101

    > df2$EVTYPE

 [1] TORNADO           EXCESSIVE HEAT    FLASH FLOOD       HEAT              LIGHTNING        
 [6] TSTM WIND         FLOOD             RIP CURRENT       HIGH WIND         AVALANCHE        
[11] WINTER STORM      RIP CURRENTS      HEAT WAVE         EXTREME COLD      THUNDERSTORM WIND
[16] HEAVY SNOW        STRONG WIND       BLIZZARD          HIGH SURF        
985 Levels:    HIGH SURF ADVISORY  COASTAL FLOOD  FLASH FLOOD  LIGHTNING ... WND

    > df2$TOTAL_INJURIES

 [1] 91346  6525  1777  2100  5230  6957  6789   232  1137   170  1321   297   309   231  1488  1021
[17]   280   805   152

I am trying to create new column called SevType -- where I will store whether a value is either an injury or fatal.

However, when I use cbind on df2$EVTYPE, it converts the factor into a numeric as seen below.

    > head(cbind(Event=df2$EVTYPE,Total = df2$TOTAL_INJURIES,Severity="INJURE"))
     Event Total   Severity
[1,] "834" "91346" "INJURE"
[2,] "130" "6525"  "INJURE"
[3,] "153" "1777"  "INJURE"
[4,] "275" "2100"  "INJURE"
[5,] "464" "5230"  "INJURE"
[6,] "856" "6957"  "INJURE"

Notice that Event at [1,] has changed from TORNADO to 834.

Any hints on why this is happening?

回答1:

We are cbinding vectors and the output will be a matrix. The matrix can hold only a single class. So, if there is any vector that is non-numeric, it will convert the whole matrix to 'character' and as the first column is already a factor, we get the numeric levels of that factor. Better would be to use data.frame

data.frame(Event=df2$EVTYPE,Total = df2$TOTAL_INJURIES,Severity="INJURE")

Or we can use bind_cols or data_frame from dplyr

来源：https://stackoverflow.com/questions/33872034/cbind-converting-factor-to-numeric

标签

cbind