Home |
Search |
Today's Posts |
#1
Posted to microsoft.public.excel.misc
|
|||
|
|||
matrix to mirror a point
Does anyone know of a generic matrix to mirror a point (x,y) about a line? I
can do this about the normal Cartesian axis but I would like to do it about a user defined line (defined by 2 points). |
#2
Posted to microsoft.public.excel.misc
|
|||
|
|||
matrix to mirror a point
Hi Paul,
I have done this in a very naive way: 1) translate the line so one point is at origin; use same translation on P 2) rotate the line by theta so it aligns with y-axis; use same rotation on P 3) generate the mirror of P (x of m = -x of p, y of m = y of p) 4) rotate everything by minus theta 5) translate by reverse amount of step 1 Hey presto, I have the old line and point plus the mirror of P Send me private message and I will forward the file Then you can do it in a more sophisticated way! best wishes -- Bernard V Liengme Microsoft Excel MVP www.stfx.ca/people/bliengme remove caps from email "Paul Jolley" wrote in message ... Does anyone know of a generic matrix to mirror a point (x,y) about a line? I can do this about the normal Cartesian axis but I would like to do it about a user defined line (defined by 2 points). |
#3
Posted to microsoft.public.excel.misc
|
|||
|
|||
matrix to mirror a point
... mirror a point (x,y) about a line? I
...I would like to do it about a user defined line (defined by 2 points). Hi. If I understand your "mirror" point, is there anything here that can help? http://mathworld.wolfram.com/Point-L...mensional.html What I'm thinking is that you know your perpendicular vector v (9), and you can just double the distance given in (11). The equation (11) appears to be correct, but I can only do it if I project r onto v, and not v onto r as I believe it's written. Note that the Determinate version in (13) is missing an implied {1,1,1} as the third argument. -- HTH :) Dana DeLouis "Paul Jolley" wrote in message ... Does anyone know of a generic matrix to mirror a point (x,y) about a line? I can do this about the normal Cartesian axis but I would like to do it about a user defined line (defined by 2 points). |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Mirror Image Printing (JSF) | Excel Discussion (Misc queries) | |||
I need more general XY point to point plotting than XY scatter in | Charts and Charting in Excel | |||
Mirror spreadsheet? | Excel Discussion (Misc queries) | |||
Mirror Image | Excel Worksheet Functions | |||
2 mirror files with :1 and :2 - why? | Excel Discussion (Misc queries) |