[R] Why is conversion not working?

[Law, Jason]

Without actually running the code, one problem seems to be that the line
if(database$year[i]>90)
is comparing a character vector to 90 and not the numbers that you are
expecting.

You could try this instead:
database$year <- as.numeric(database$year)
ifelse(database$year > 90, database$year + 1900, database$year + 2000)

Jason Law
Statistician
City of Portland, Bureau of Environmental Services
Water Pollution Control Laboratory
6543 N Burlington Avenue
Portland, OR 97203 -5452
jlaw at bes.ci.portland.or.us



-----Original Message-----
From: r-help-bounces at r-project.org
[mailto:r-help-bounces at r-project.org]On Behalf Of Jonas Malmros
Sent: Monday, December 17, 2007 4:53 PM
To: r-help at r-project.org
Subject: [R] Why is conversion not working?


I have a data frame, where two last columns - "month" and "year" - are
character vectors. The "year" vector is made of two numbers (i.e. "97"
for 1997, "07" for 2007, etc)
What I want to do is to create a variable "Year" that is mode numeric
and where each record is a four-figure number (1997, 2007,...)
I have about 40000 rows in the dataframe, the observations are for 10
years (so there are multiple rows for each year).
I tried the following, but the program runs and runs, and if I abort
it all the years in "Year" are 1997:

for(i in 1:dim(database)[1]){
    if(database$year[i]>90) {
           database$Year[i] <- as.numeric(database$year[i])+1900 } else {
           database$Year[i] <- as.numeric(database$year[i])+2000
    }
}

Thanks in advance for explanations.

Regards,
JM

-- 
Jonas Malmros
Stockholm University
Stockholm, Sweden

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