R help - Dec 2009 - Replace values in a vector

Hi all,

I have a vector like this:

x<- c(0.7, 0.1, 0, 0.2, 0.2, 0, 0, 0 , 0, 0.4, 0, 0.8, 1.8)

I would like  to replace the zero values with the first previous non zero value.

my returning vector should look like this:

y<-c( 0.7, 0.1, 0.1,0.2,0.2,0.2,0.2,0.2, 0.4, 0.4, 0.8, 1.8)

How can I do this in R without using for loop?

Thank you

na.locf in the zoo package takes the last occurrence and carries it forward
into NAs so replace your zeros with NAs and then apply na.locf like this:

   library(zoo)
   na.locf(replace(x, x==0, NA))


On Thu, Dec 3, 2009 at 11:41 AM, Farida Mostajabi
<f0most01@louisville.edu>wrote:
> Hi all,
>
> I have a vector like this:
>
> x<- c(0.7, 0.1, 0, 0.2, 0.2, 0, 0, 0 , 0, 0.4, 0, 0.8, 1.8)
>
> I would like  to replace the zero values with the first previous non zero
> value.
>
> my returning vector should look like this:
>
> y<-c( 0.7, 0.1, 0.1,0.2,0.2,0.2,0.2,0.2, 0.4, 0.4, 0.8, 1.8)
>
> How can I do this in R without using for loop?
>
> Thank you
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

WOW! It worked. Thank you!
>>> Gabor Grothendieck <ggrothendieck at gmail.com> 12/03/09
11:46 AM >>>
na.locf in the zoo package takes the last occurrence and carries it forward
into NAs so replace your zeros with NAs and then apply na.locf like this:

   library(zoo)
   na.locf(replace(x, x==0, NA))


On Thu, Dec 3, 2009 at 11:41 AM, Farida Mostajabi
<f0most01 at louisville.edu>wrote:
> Hi all,
>
> I have a vector like this:
>
> x<- c(0.7, 0.1, 0, 0.2, 0.2, 0, 0, 0 , 0, 0.4, 0, 0.8, 1.8)
>
> I would like  to replace the zero values with the first previous non zero
> value.
>
> my returning vector should look like this:
>
> y<-c( 0.7, 0.1, 0.1,0.2,0.2,0.2,0.2,0.2, 0.4, 0.4, 0.8, 1.8)
>
> How can I do this in R without using for loop?
>
> Thank you
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Farida Mostajabi
> Sent: Thursday, December 03, 2009 8:41 AM
> To: r-help at r-project.org
> Subject: [R] Replace values in a vector
> 
> Hi all,
> 
> I have a vector like this:
> 
> x<- c(0.7, 0.1, 0, 0.2, 0.2, 0, 0, 0 , 0, 0.4, 0, 0.8, 1.8)
> 
> I would like  to replace the zero values with the first 
> previous non zero value.
> 
> my returning vector should look like this:
> 
> y<-c( 0.7, 0.1, 0.1,0.2,0.2,0.2,0.2,0.2, 0.4, 0.4, 0.8, 1.8)
y is shorter than x.  Shouldn't there be a run of 6 0.2s,
not 5?
 
> How can I do this in R without using for loop?
One way is
   > isNotZero <- function(x) !is.na(x) & x!=0
   > f<-function(x)x[cummax(seq_along(x) * isNotZero(x))]
   > f(x)
    [1] 0.7 0.1 0.1 0.2 0.2 0.2 0.2 0.2 0.2 0.4 0.4 0.8 1.8
This one drops an initial run of 0's but could be adjusted
to do something with them.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com 
 
> Thank you
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Yes, should be 6  0.2.  The code worked. Thank you!
>>> William Dunlap <wdunlap at tibco.com> 12/03/09 12:07 PM
>>>
> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Farida Mostajabi
> Sent: Thursday, December 03, 2009 8:41 AM
> To: r-help at r-project.org
> Subject: [R] Replace values in a vector
> 
> Hi all,
> 
> I have a vector like this:
> 
> x<- c(0.7, 0.1, 0, 0.2, 0.2, 0, 0, 0 , 0, 0.4, 0, 0.8, 1.8)
> 
> I would like  to replace the zero values with the first 
> previous non zero value.
> 
> my returning vector should look like this:
> 
> y<-c( 0.7, 0.1, 0.1,0.2,0.2,0.2,0.2,0.2, 0.4, 0.4, 0.8, 1.8)
y is shorter than x.  Shouldn't there be a run of 6 0.2s,
not 5?
 
> How can I do this in R without using for loop?
One way is
   > isNotZero <- function(x) !is.na(x) & x!=0
   > f<-function(x)x[cummax(seq_along(x) * isNotZero(x))]
   > f(x)
    [1] 0.7 0.1 0.1 0.2 0.2 0.2 0.2 0.2 0.2 0.4 0.4 0.8 1.8
This one drops an initial run of 0's but could be adjusted
to do something with them.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com 
 
> Thank you
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>