[R] Increment certain values in a vector

Thomas Chesney Thomas.Chesney at nottingham.ac.uk
Thu Oct 1 13:29:29 CEST 2015


I got it sorted thank you. As you point out, the original code works fine (there was a type mismatch with it).


On 1 Oct 2015, at 12:00, PIKAL Petr <petr.pikal at precheza.cz> wrote:

Hi

Are agents and agent different objects? Or it is a typo? Better would be to provide some real or fake data by dput or at least result of str(agent) and str(agents)

Actually your code shall work in case agent and agents have same length and expected order.

agents[which(agent$membership == 1)] <- agents[which(agent$membership == 1)] + 1

For less typing you can do:

sel <- which(agent$membership == 1)
agents[sel] <- agents[sel] + 1

The code can be different if agent or agents are objects like matrix or array. Actually from the code xxx$yyy I presume it is data frame or list.

Cheers
Petr


> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Thomas
> Chesney
> Sent: Thursday, October 01, 2015 12:04 PM
> To: r-help at r-project.org
> Subject: [R] Increment certain values in a vector
> 
> How can I manipulate values of only certain entries in a vector, based
> on what the existing values are?
> 
> So for instance if I want to add one to each of the following values,
> or multiply them by a specific factor:
> 
> agents[which(agent$membership == 1)]
> 
> how would I do this please?
> 
> If there was just one value to manipulate I'd just do this:
> 
> value <- value + 1
> 
> and this would let me set the values:
> 
> agents[which(agent$membership == 1)] <- 100
> 
> but how to essentially achieve this:
> 
> agents[which(agent$membership == 1)] <- agents[which(agent$membership
> == 1)] + 1
> 
> Thank you!
> 
> 
> 
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