[R] Strange subvector output --> x[n] != x[1:n][n]

Jeff Newmiller jdnewmil at dcn.davis.CA.us
Fri Dec 20 08:28:38 CET 2013


Sigh. Google couldn't help you?

Try FAQ 7.31 and then use non-fractions to generate sequences... scale as desired. This is not unique to R.
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Sent from my phone. Please excuse my brevity.

Gewart <gewart at biotron.com.au> wrote:
>Hi, Can anyone explain what is going on...!?   For a vector
>"x=seq(min,max,0.01)", when generating sub-vector "a" based on a
>starting
>value "st", things go as expected as long as "st" is not too close to
>the
>beginning of "x".  For example, if x starts at -5 and increments by
>0.01,
>whenever I try to generate the sub-vector "a" (as below) with a
>starting
>value of 0.49 or less it does not generate the expected output: The
>initial
>value of "a" is wrong.
> 
>Thanks in advance for any clarity you can shed.
>Gary
>
>...(please see two versions of code below).... 
>
>#THIS WORKS...(st > -4.9)
>
>	min = -5; max = 1;  x=seq(min,max,0.01)
>
>	st= -4.8 ; end= 0    
>
>	a=x[((st-min)/0.01+1):((end-min)/0.01+1)] 
>	
>			n=(st-min)/0.01+1
>#compare	
>	a[1:10]; c(x[n:(n+9)])
>
>#test...
>	n
>	x[1:n]; x[n]           ### x[n]== x[1:n][n] ; As expected
>##########################################################
>#  BUT THIS IS WEIRD!!...(st <= -4.9)
>	
>	st= -4.90 ; end= 0     ### -> BUG in generation of a!!
>
>	a=x[((st-min)/0.01+1):((end-min)/0.01+1)]; 
>	
>			n=(st-min)/0.01+1
>#compare	
>	a[1:10]; c(x[n:(n+9)])
>#test
>	n
>	x[1:n]; x[n]  ### NOW x[n] != x[1:n][n]   !!?? What is going on!?
>
>
>
>
>
>--
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>http://r.789695.n4.nabble.com/Strange-subvector-output-x-n-x-1-n-n-tp4682526.html
>Sent from the R help mailing list archive at Nabble.com.
>
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