[R-sig-Geo] Dont show zero values in line graph

[Rainer M Krug]

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On 01/07/2011 11:56 AM, Edzer Pebesma wrote:
> 
> 
> On 01/07/2011 09:43 AM, Rainer M Krug wrote:
>> On 01/07/2011 08:43 AM, Edzer Pebesma wrote:
>>
>>
>>> On 01/07/2011 04:11 AM, jroll wrote:
>>>>
>>>> Hey everyone,
>>>>    Im getting better at plotting my data but cant for the life of me figure
>>>> out how to show a line graph with missing data that doesnt continue the line
>>>> down to zero then back up to the remaining values.
>>>>
>>>> Consider the following
>>>> x<-c(1:5,0,0,8:10)
>>>> y<-1:10
>>>>
>>>> plot(0,0,xlim=c(0,10), ylim=c(0,10),type="n",main="Dont show the bloody 0
>>>> values!!")
>>>> lines(x~y, col="blue", lwd=2,)
>>>>
>>>> My data is missing the 6th and 7th values and they come in as NA's so i
>>>> change them to 0s but then the plot has these ugly lines that dive toward
>>>> the x axis then back up.  I would do bar plots but i need to show multiple
>>>> sets of data on the same and side by side bars doesnt do it for me.  
>>>>
>>>> So i need a line graph that starts and stops where 0s or missing values
>>>> exist.  Thoughts?
>>
>>> x<-c(1:5,NA,NA,8:10)
>>> y<-1:10
>>
>>> plot(0,0,xlim=c(0,10), ylim=c(0,10),type="n",main="Dont show the bloody 0
>>> values!!")
>>> lines(x~y, col="blue", lwd=2,)
>>
>> And just to complete it: to replace all the 0 in x with NA, you can do
>>
>> x[x==0] <- NA
>>
>> There is also the is.na() function which should do this, i.e.
>>
>> is.na(x) <- 0
>>
>> should (in my understanding) set all 0 values in x to NA - but it dose
>> not work, whereas setting e.g. all the 4s to NA works:
>>
>>> x<-c(1:5,0,0,8:10)
>>> is.na(x) <- 0
>>> x
>>  [1]  1  2  3  4  5  0  0  8  9 10
>>> is.na(x) <- 4
>>> x
>>  [1]  1  2  3 NA  5  0  0  8  9 10
>>
>>
>> Why is this? Is this a bug in R or in y understanding?
> 
> try ?is.na:

I did ...

> 
> Usage:
> 
>      NA
>      is.na(x)
>      ## S3 method for class 'data.frame'
>      is.na(x)
> 
>      is.na(x) <- value
> 
> Arguments:
> 
>        x: an R object to be tested: the default method handles atomic
>           vectors, lists and pairlists.
> 
>    value: a suitable index vector for use with ‘x’.

but my understanding of is.na() modified the help.
Thanks for pointing this out - now I know how I can use
is.na(...) <- ...

> 
> so,
> 
> is.na(x) <- 0
> 
> does nothing, as 0 is not a suitable index vector:

Absolutely true.

> 
>> x = 1:10
>> x[0]
> integer(0)
> 
> x[5] = 0
> is.na(x) <- x == 0
> x
>  [1]  1  2  3  4 NA  6  7  8  9 10
> 
> does what you wanted, I believe.

Yes - thanks a lot.

> 
>>
>> Cheers,
>>
>> Rainer
>>
>>>>
>>>> JR 
>>
>>
>>
> 


- -- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology, UCT), Dipl. Phys. (Germany)

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