Re: [Jprogramming] Matrix of functions

[Lippu Esa]

Hello

I played some years ago with 2D rotation as part of general linear mappnigs 
with complex numbers.

A small demo below.

Esa

NB. ID rotdemo.ijs v0.0 28.06.17

NB. NO rotate some points

load 'graph'

tographcoord=:[:_0.98&+1.96&*

randompts=. 3 : 0
(y,2) $ tographcoord ?(+:y) #0
)

rot=: 4 : 0
+.(j./"1 x)*^j.y
)

]data=:randompts 20

rotloop=: 4 : 0
i=.0
while. i<y
do.
RED gdrect gddraw (x rot 0.01*i),"(1) 0.02 0.02
i=.>:i
wd 'msgs'
end.
)

data rotloop 1256


-----Original Message-----
From: Programming <programming-boun...@forums.jsoftware.com> On Behalf Of 
Francesco Pedulla'
Sent: Friday, December 18, 2020 9:59 AM
To: programm...@jsoftware.com
Subject: [Jprogramming] Matrix of functions

Dear all,
I need to represent the 2D rotation matrix 'R'

R = |cos(t)  -sin(t)|
       |sin(t)   cos(t)|

and compute it for different values of the rotation angle 't'. I am aware
the matrix of function can be represented as a gerund, which I like:

R =: 2 2$cos`(-@sin)`sin`cos .

To compute R(t), I wrote the following definition:

mf =: conjunction : '($x)$,(,x)/.((+/$x)$y)'


so that "R mf pi%4" returns R(pi/4). But I find the code for 'mf' not very
elegant. Is there a better way to achieve this?
Thanks in advance for any hint,

Francesco
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