Heinz,
<disclaimer>
VERY LONG
</disclaimer>
:)
I've found that the gca() (get current axes) handle allows to see and
control many properties. First run this example:
x = (0:360)/180*%pi;
y = 0.5*(1 + cos(x));
z = 0.5 + 0.5*(1 + cos(x));
clf
polarplot([x' x'],[y' z'],[1 2])
Entering
gca()
one of the entities included in the handle are the children. Among much
other information there is
children: matrix 34x1.
With
gca().children
you get a hint. The answer is:
34 by 1 matrix of handles:
==========================
Text
Segs
Text
Segs
(...)
Text
Arc
Compound
Exactly 34 rows. Yo can see what's inside any one of them by means of,
for instance,
gca().children(1)
The answer starts
Handle of type "Text" with properties:
======================================
parent: Axes
children: []
visible = "on"
text = "330"
alignment = "left"
data = [1.3825602,-0.7982215,0]
(...)
This says it has a "parent" Axes (it is logical, since this is one of
the "children" of the current axes), no children (no subordinated
structure), it is visible, its text is "330", it is lefy aligned, and
its coordinates are
(x,y,z) = [1.3825602,-0.7982215,0]
They can be retrieved as a variable by means of
gca().children(1).data
It is easy to check that these coordinates represent an angle of 330°
and a radius slightly larger than the radius of the polar plot border
circumference (by simple inspection, 1.5). This radius can be calculated as
Rtext = sqrt(sum(gca().children(1).data.^2))
One can change the position and the text to be displayed, for instance,
to locate the text "NNE" at -22.5°,
theta = -22.5/180*%pi;
gca().children(1).data = Rtext*[cos(theta), sin(theta), 0];
gca().children(1).text = "NNE";
Next is to control the radial lines. These are in children(2). Typing
gca().children(2)
gives the following answer:
Handle of type "Segs" with properties:
======================================
parent: Axes
children: []
visible = "on"
data = [0,0,0;1.3858193,-0.5740251,0]
line_mode = "on"
(...)
The field data represent the coordinates of the extremes of the radial
lines:
0. 0. 0.
1.3858193 -0.5740251 0.
so the radius is the length:
A = gca().children(2).data;
R = sqrt((A(2, :)- A(1, :)).^2);
You can modify the angle this way:
theta = -22.5/180*%pi;
gca().children(2).data(2, :) = R * [cos(theta), R*sin(theta), 0];
This can be repeated with other children, for instance children(3)
contains the second text and children(4) the second radial line.
Most of this information can be discovered typing
apropos entities
which leads to the graphic entities help. It is very ramified and very
long, but it is worth it...
There is stil a problem I could not solve, i.e., there are only 24
children, corresponding 12 to text and 12 to radius, and for a windrose
you need 16 of each. The other children correspond to the circumference
arcs of the rho grid of the polar plot.
I don't know how to add or insert more children to the graphic handle...
One possible way (very risky, ensure you make a backup first or work
with a different function name) is try to find the source for the
function polarplot and see where is the definition of the number of
labels and try to customize the function.
Regards,
Federico Miyara
On 27/03/2019 17:37, Heinz Nabielek wrote:
Friends and colleagues:
Scilab polarplot does a great job displaying my 155,508 measured data pairs
wind direction/ wind speed in a split second( while MS Excel is petrified) to
make a great wind rose.
One concern: I would like to change the default 30° ray separation into 22.5°
separations to indicate N, NNE, NE, ENE, E .... directions.
How can I do that?
Best greetings
Heinz
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