setting a number of values to NA over a data.frame.

--- Petr Pikal <petr.pikal at precheza.cz> wrote:

Hi

Strange. It works for me without any problem.

The problem is that my dataframe has 1,s in about 50%
of the columns and I only want it to apply to a few
specified columns. My explanation may not have been
clear enough.

Using your example,I want all values for tio2 set to 1
but not any values in al2o3 whereas zeta[zeta==1]<-NA
is also changing al2o3[3] to NA.

Thanks

zeta

  tepl tio2 al2o3  iep
1   60    1   3.5 5.65
2   60    1   2.0 5.00
3   60    1   1.0 5.30
4   60    0   2.0 4.65
5   40    1   3.5 5.20
6   40    1   2.0 4.85
7   40    0   3.5 5.70
8   40    0   2.0 5.25

zeta[zeta==1]<-NA
zeta

  tepl tio2 al2o3  iep
1   60   NA   3.5 5.65
2   60   NA   2.0 5.00
3   60   NA    NA 5.30
4   60    0   2.0 4.65
5   40   NA   3.5 5.20
6   40   NA   2.0 4.85
7   40    0   3.5 5.70
8   40    0   2.0 5.25

str(zeta)

'data.frame':   8 obs. of  4 variables:
 $ tepl : int  60 60 60 60 40 40 40 40
 $ tio2 : num  NA NA NA 0 NA NA 0 0
 $ al2o3: num  3.5 2 NA 2 3.5 2 3.5 2
 $ iep  : num  5.65 5 5.3 4.65 5.2 4.85 5.7 5.25

HTH
Petr



On 7 Feb 2007 at 16:57, Erik Iverson wrote:

Date sent:      	Wed, 07 Feb 2007 16:57:40 -0600
From:           	Erik Iverson
<iverson at biostat.wisc.edu>
To:             	John Kane <jrkrideau at yahoo.ca>
Copies to:      	R R-help <r-help at stat.math.ethz.ch>
Subject:        	Re: [R] setting a number of values
to NA over  a data.frame.

John -

Your initial problem uses 0, but the example uses

1 for the value that

gets an NA.  My solution uses 1 to fit with your

example.  There may

be a better way, but try something like

data1[3:5] <- data.frame(lapply(data1[3:5],

function(x) ifelse(x==1,

NA, x)))

The data1[3:5] is just a test subset  of columns I

chose from your

data1 example.  Notice it appears twice, once on

each side of the

assignment operator.

In English, apply to each column of the data frame

(which is a list) a

function that will return NA if the element is 1,

and the value

otherwise, and then turn the modified lists into a

data.frame, and

save it as data1.



See the help files for lapply and ifelse if you

haven't seen those

before.

Maybe someone has a better way?

Erik

John Kane wrote:

This is probably a simple problem but I don't

see a

solution.

I have a data.frame with a number of columns

where I

would like 0 <- NA

thus I have df1[,144:157] <- NA if df1[, 144:

157] ==0

and df1[, 190:198] <- NA if df1[, 190:198] ==0

but I cannot figure out a way do this.  

cata <- c( 1,1,6,1,1,NA)
catb <- c( 1,2,3,4,5,6)
doga <- c(3,5,3,6,4, 0)
dogb <- c(2,4,6,8,10, 12)
rata <- c (NA, 9, 9, 8, 9, 8)
ratb <- c( 1,2,3,4,5,6)
bata <- c( 12, 42,NA, 45, 32, 54)
batb <- c( 13, 15, 17,19,21,23)
id <- c('a', 'b', 'b', 'c', 'a', 'b')
site <- c(1,1,4,4,1,4)
mat1 <-  cbind(cata, catb, doga, dogb, rata,

ratb,

bata, batb)

data1 <- data.frame(site, id, mat1)
data1

 # Obviously this works fine for one column

data1$site[data1$site ==1] <- NA  ; data1

but I cannot see how to do this with indices

that

would allow me to do more than one column in the
data.frame.

At one point I even tried something like this
a <- c("site")
data1$a[data1$a ==1] <- NA

which seems to produce a corrupt data.frame.

I am sure it is simple but I don't see it.  

Any help would be much appreciated.

provide commented,

minimal, self-contained, reproducible code.

provide commented,

minimal, self-contained, reproducible code.

Petr Pikal
petr.pikal at precheza.cz