[R] Read a txt file as numeric

[arun]

Hi,
May be this helps:
dat1<- read.table(text="
142,QUANTIZE_CAL_MIN_BAND_10,1
143,QUANTIZE_CAL_MAX_BAND_11,65535
144,QUANTIZE_CAL_MIN_BAND_11,1
145,END_GROUP,MIN_MAX_PIXEL_VALUE
146,GROUP,RADIOMETRIC_RESCALING
147,RADIANCE_MULT_BAND_1,1.2483E-02
148,RADIANCE_MULT_BAND_2,1.2730E-02
",sep=",",header=FALSE,stringsAsFactors=FALSE,row.names=1)

#Assuming that 142, 143, etc are row.names.
#You could create a new column with just the numeric values leaving the strings in the 2nd column.
dat1$NewCol<-as.numeric(ifelse(grepl("\\d+",dat1[,2]),dat1[,2],NA))
dat1[,2][grepl("\\d+",dat1[,2])]<-NA
dat1
#                          V2                    V3     NewCol
#142 QUANTIZE_CAL_MIN_BAND_10                  <NA> 1.0000e+00
#143 QUANTIZE_CAL_MAX_BAND_11                  <NA> 6.5535e+04
#144 QUANTIZE_CAL_MIN_BAND_11                  <NA> 1.0000e+00
#145                END_GROUP   MIN_MAX_PIXEL_VALUE         NA
#146                    GROUP RADIOMETRIC_RESCALING         NA
#147     RADIANCE_MULT_BAND_1                  <NA> 1.2483e-02
#148     RADIANCE_MULT_BAND_2                  <NA> 1.2730e-02
 str(dat1)
#'data.frame':    7 obs. of  3 variables:
# $ V2    : chr  "QUANTIZE_CAL_MIN_BAND_10" "QUANTIZE_CAL_MAX_BAND_11" "QUANTIZE_CAL_MIN_BAND_11" "END_GROUP" ...
# $ V3    : chr  NA NA NA "MIN_MAX_PIXEL_VALUE" ...
# $ NewCol: num  1 65535 1 NA NA ...

A.K.


Hello, 

I am relatively new to the R community. 
I have a .txt file containing the metafile with informations 
regarding landsat calibration parameters. This contains 2 columns: one 
with the description of the parameter and the other one with the value 
of the parameter. The problem is that the column with the values 
contains also words in some cases, which I believe makes the 
read.table() read the column not as a numeric value. 
This is an example of how it looks like: 

142           QUANTIZE_CAL_MIN_BAND_10                                              1 142 
143           QUANTIZE_CAL_MAX_BAND_11                                          65535 143 
144           QUANTIZE_CAL_MIN_BAND_11                                              1 144 
145                          END_GROUP                            MIN_MAX_PIXEL_VALUE 145 
146                              GROUP                          RADIOMETRIC_RESCALING 146 
147               RADIANCE_MULT_BAND_1                                     1.2483E-02 147 
148               RADIANCE_MULT_BAND_2                                     1.2730E-02 148 
149               RADIANCE_MULT_BAND_3                                     1.1656E-02 149 

I need the left column to be read as numeric, does anyone have some good suggestion on how to approach this problem? 

Thank you in advance. 

Stefano