Loading in Large Dataset + variables via loop

Hi Rui,

Getting some error messages:


varNames <- as.vector(apply(colNames, 1, paste, collapse=""))
Error in apply(colNames, 1, paste, collapse = "") :
   dim(X) must have a positive length

A.K.



----- Original Message -----
From: Rui Barradas <ruipbarradas at sapo.pt>
To: cmc0605 <colose21 at gmail.com>
Cc: r-help at r-project.org
Sent: Sunday, July 15, 2012 8:12 AM
Subject: Re: [R] Loading in Large Dataset + variables via loop

Hello,

Why do you need 9 variables in your environment if they are time series
that correspond to the same period? You should use time series functions.

#install.packages('zoo')
library(zoo)

# Make up a dataset
Year <- seq(from=as.Date("1901-01-01"), by="year", length.out=100)
dat <- data.frame(matrix(rnorm(100*9), ncol=9), Year)

# assign names.
varNames <- expand.grid(c("temp", "precip", "pressure"), 1:3,
stringsAsFactors=FALSE)
varNames <- as.vector(apply(colNames, 1, paste, collapse=""))
varNames <- c(varNames, "Year")
names(dat) <- varNames
head(dat)

# and transform it into a time series of class 'zoo'
z <- zoo(dat[, 1:9], order.by=dat$Year)
str(z)
head(z)


Another way would be, like you say, to use a loop to put the variables
in a list. Something like

lst <- list()
for(i in 1:9) lst[[i]] <- dat[, i]
names(lst) <- varNames


Note that I've used a dataset called 'dat' n place of your 'A'. You
should post a data example, like the posting guide says. Using dput().

Hope this helps,

Rui Barradas



Em 14-07-2012 03:44, cmc0605 escreveu:

Hello, I'm new to R with a (probably elementary) question.

Suppose I have a dataset called /A/ with /n/ locations, and each location
contains within it 3 time series of different variables (all of 100 years
length); each time series is of a weather variable (for each location there
is a temperature, precipitation, and pressure).  For instance, location 1
has a temperature1 time series, a precip1 time series, and a pressure1 time
series; location two has a temperature2, precip2, and pressure2
timeseries...That is, there are 100 rows, and (/n/*3)+1 columns.  The extra
column is the time.

I want to load in this dataset and declare a variable for each time series.
The columns are in order of location, so it goes temp1, precip1,pressure1,
temp2,... and so forth in increasing column order.  There are always 100
rows.  Manually, Id have to do:

temp1=A[,1]
precip1=A[,2]
pressure1=A[,3]
temp2=A[,4]
precip2=A[,5]
pressure2=A[,6]
temp3=A[,7]
and so forth.....

Problem is, n is large, so I don't want to repeat this pattern forever.  I
figure I need a loop both for the variable name (ie.., the variable at a
particular location) as well as for what column it reads from.

Any help...?



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