[R] Draw a perpendicular line?

[baptiste auguie]

hi,

also, make sure you have set the aspect ratio to 1:1 when plotting (asp=1).

HTH,

baptiste

On 25 August 2010 10:20, Benno Pütz <puetz at mpipsykl.mpg.de> wrote:
> Maybe
>
> perp.slope = -1/slope
> abline(cy - cx*perp.slope, perp.slope)
>
> where cx, cy are x- and y-coordinate of C, resp., and slope the slope you calculated for the line through A and B
>
>
> Am 24.Aug.2010 um 0:04 schrieb CZ:
>
>>
>> Hi,
>>
>> I am trying to draw a perpendicular line from a point to two points.
>> Mathematically I know how to do it, but to program it, I encounter some
>> problem and hope can get help.  Thanks.
>>
>> I have points, A, B and C.  I calculate the slope and intercept for line
>> drawn between A and B.
>> I am trying to check whether I can draw a perpendicular line from C to line
>> AB and get the x,y value for the point D at the intersection.
>>
>> Assume I get the slope of the perpendicular line, I will have my point (D)
>> using variable x and y which is potentially on line AB.   My idea was using
>> |AC|*|AC| = |AD|*|AD|+ |CD|*|CD|.  I don't know what function I may need to
>> call to calculate the values for point D (uniroot?).
>>
>> Thank you.
>>
>>
>>
>> --
>> View this message in context: http://r.789695.n4.nabble.com/Draw-a-perpendicular-line-tp2335882p2335882.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
>> ______________________________________________
>> 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.
>>
>
> ______________________________________________
> 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.
>



-- 
____________________

Dr. Baptiste Auguié

Departamento de Química Física,
Universidade de Vigo,
Campus Universitario, 36310, Vigo, Spain

tel: +34 9868 18617
http://webs.uvigo.es/coloides