Re: Difficulty with createLine

[Thomas D. Dean]

On 06/02/2016 01:41 PM, Thomas D. Dean wrote:
> I have two scripts that create lines, using the same data, but different
> calls and I get different lines when I think I should be getting the
> same line.
>
> The first set of data comes from a complicated calculation.
>
> octave:1027> relTgtPosit
> relTgtPosit =
>
>     95.0000   16.0000
>     80.2279   -3.8953
>     65.4558  -23.7906
>     53.4611  -31.3488
>     29.4717  -46.4653
>      5.4823  -61.5818
> relTgtLeg =
> createLine([relTgtPosit(1,:),relTgtPosit(3,:);relTgtPosit(3,:),relTgtPosit(6,:)])

relTgtPoist was created as an array of points.  I think Octave 
simplified this array.  In this call to createLine, I am passing an 
array with 4 values per row and createLine treats the 4 values as 
[x,y,dx,dy] when I thought I was passing [P1, P2].  sigh.
I should call

createLine(relTgtPosit(1,1),relTgtPosit(1,2),...
 relTgtPosit(3,1)-relTgtPosit(1,1),...
 relTgtPosit(3,2)-relTgtPosit(1,2))
createLine(relTgtPosit(4,1),relTgtPosit(4,2),...
 relTgtPosit(6,1)-relTgtPosit(4,1),...
 relTgtPosit(6,2)-relTgtPosit(4,2))

or, is this the best I can to to vectorize this?
idx=[1;4]; ## how do I generalize this???
createLine(relTgtPosit(idx,1),relTgtPosit(idx,2),...
 relTgtPosit(idx+2,1)-relTgtPosit(idx,1),...
 relTgtPosit(idx+2,2)-relTgtPosit(idx,2))

> The second set of data comes from direct assignment
>
> T1 = [95.0000   16.0000]
> T2 = [80.2279   -3.8953]
> T3 = [65.4558  -23.7906]
> lineT = createLine(T1,T3);

In this call to createLine, I am passing two points and createLine does 
the right thing.

> figure; hold on; axis([0 120 -80 20]);
> grid
> drawLine(relTgtLeg(1,:), 'color', 'b')
> drawLine(lineT, 'color', 'c')
> hold off