[R] How to convert a character string to a number

[Stephen D. Weigand]

Dear Andreas,

On May 23, 2005, at 4:56 AM, Kraft, Andreas wrote:

> Hi everyone,
> I have a simple problem but don´t know how to solve it.
> I read in a table from a text file that looks like that:
>
> -3,932200E-01   -2,000000E-01   4,999995E-02
> -3,932099E-01   -1,000000E-01   3,999996E-02
...
> -3,931300E-01   0,000000E+00  3,499996E-02
>
> but when I try to to plot the values from the
> second column, the plot shows the wrong values.
>
> That's what I do in R:
> read.table("C:\\Messdaten\\epp1_1_ver.txt")->sh1
>

Read the help for read.table() and use dec = ",".

Also, before you correct the call to read.table, if you enter

R> str(sh1)

you'll see something like:

R> str(sh1)
`data.frame':	10 obs. of  3 variables:
  $ V1: Factor w/ 10 levels "-3,931300E-01",..: 10 9 8 7 6 5 4 3 2 1
  $ V2: Factor w/ 5 levels "-1,000000E-01",..: 2 1 4 1 1 5 3 4 4 4
  $ V3: Factor w/ 5 levels "2,499996E-02",..: 5 3 3 4 4 2 3 1 1 2

which gives you some very helpful information.  In particular, it
shows that sh1 consists of factors.

Good luck,

Stephen


>> sh1[1:10,2]
>
>  [1] -2.000000E-01 -1.000000E-01 0.000000E+00  -1.000000E-01 
> -1.000000E-01 3.000000E-01  -3.000000E-01 0.000000E+00
>
>  [9] 0.000000E+00  0.000000E+00
>
> 1707 Levels: -1,000000E-01 -1,000000E+00 -1,000000E+01 -1,002000E+02 
> -1,003000E+02 -1,004000E+02 ... 9,980000E+01
>
>> sh1[1:10,2]->a
>
>> cbind(x=seq(1,10,by=1),y=a)
>
>        x    y
>
>  [1,]  1  436
>
>  [2,]  2  321
>
>  [3,]  3 1007
>
>  [4,]  4  321
>
>  [5,]  5  321
>
>  [6,]  6 1353
>
>  [7,]  7  548
>
>  [8,]  8 1007
>
>  [9,]  9 1007
>
> [10,] 10 1007
>
>
>
> Why do I get those values? Why is for example -2,000000E-01 equal to 
> 436?
>
> I need to convert the values from -2,000000E-01 to -0.2  - how can I 
> do this?
>
>
>
> Thank you for your suggestions,
>
>
>
> Andreas Kraft
>
>
>
>
> 	[[alternative HTML version deleted]]
>
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