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# Nan value is stuck

in General Posts: 13

I have two variables x,y that are calculating very small numbers between 0 and 1 depending on variables a and b. It is understandable that the values are going to sometimes come up as "nan". However, when I set a and b to values that make x or y a small number, then a value that computes nan for x or y, then set a or b back to what should compute a small number again, the values stay as nan. The project is running while doing those steps. Can someone try this out to see if it's a bug, or just a problem in my code? Or teach me how to round to the nearest nth?

Tagged:

• edited August 2016 Posts: 7,834

@PlatniumFrog If you want to check if a value is `nan`, then check the value against itself. If it's not equal to itself, it's `nan`.

``````function setup()
a=0/0
print(a)
if a~=a then
print("a = nan, setting a to 0")
a=0
end
print("a = ",a)
end
``````
• Posts: 5,396

If you still have problems, post the code

• Posts: 13

Could I have a function that rounds an oversized decimal to the maximum number of decimal places a number can have in codea/lua?

• edited August 2016 Posts: 7,834

Here's a routine. Pass it a number and how many decimal places you want. Just figure out how many decimal places you want. If you always want a fixed number of decimal places, replace dp with that value.

EDIT: The number of decimal places you can have will depend on how many digits are before the decimal point.

EDIT: With this routine, it looks like you can have a total of 14 digits.

``````function setup()
a=123.45678901645678912
b=round(a,8)
print(b)
end

function round(val,dp)
return((val*10^dp+0.5)//1)/10^dp
end
``````
• edited August 2016 Posts: 13

Here is what I have been trying to build.
The forum post handler leaves out multiplication stars and auto detects code which personally is slightly annoying Ths means that to use this while in the codea editor, you will have to insert a multiplication star inbetween joined variables.
Obviously all varibles are defined in the setup function so you will have no trouble.
Code starts here and ends before "code stops":

``````-- Fractler
-- This draws a mandlebrot fractal and later will draw custom fractals given a mathimatical formula
-- code is translated to lua from the code discussed in this video:
-- -- Use this function to perform your initial setup
function setup()
-- canvas x and y values
canX = 175
canY = 175

-- the shapes that can be drawn are "point", "circle", and "rect"
shape = "rect"

-- values used for mathimatical formulas
-- (I haven't gotten the fornula right...)
x = 0
y = 0
a = -2
b = -2

-- res is a value between 0 and 1 that is how detailed the fractal renders
res = 0.05

-- this table contains "valid" points and is explained later
points = {}

-- this bool tell wether the fractal is done rendering
finished = false

-- this is used to tell where to add walues to "points"
key = 0
end
-- functions separator and console are going to be used later for creating custom fractals
function separator()
pushStyle()
pushMatrix()
strokeWidth(5)
stroke(0, 0, 0, 128)
line(200,0,200,HEIGHT)
popMatrix()
popStyle()
end
function console()
s = keyboardBuffer()
pushStyle()
pushMatrix()
textAlign(LEFT)
textWrapWidth(180)
fill(0, 0, 0, 128)
fontSize(20)
text(s,20,(HEIGHT/2)+200)
popMatrix()
popStyle()
end
-- the function below has not been implemented
-- function round(val,dp)
-- return((val*10^dp+0.5)//1)/10^dp
-- end
-- This function gets called once every frame
function diverges()
-- the point at which the mandlebrot set diverges
-- is 2 from the center
if (x*x)+(y*y) < 4 then
return true
else
return false
end
end

function iterate(n)
-- this function contains formulas that can be called over and over again
-- to iterate
for i=0,1,n do
local tmp = (x*x) - (y*y) + a
y = (x*y) + (x*y) + b
x = tmp
end
end

function draw()
--[[if CurrentTouch.state == BEGAN
and CurrentTouch.x <= 200 then
showKeyboard()
end]]
-- This sets a light background color
background(0, 11, 25, 255)
-- this draws all the points that are within the fractal
for i=0,1,res do
iterate(res) -- this iterates the mathimatical funtion for each
-- value of "a" and "b"
if finished == false then
-- this makes "a" and "b" go through all values
-- between 2 and -2
if a <= 2 then
a = a + res
end
if a >= 2 then
if b <= 2 then
a = -2
b = b + res
end
end
if b >= 2 then
-- this discontiues the loop by setting "finished"
-- to "true" when the loop requires it to be "false"
finished = true
a = -2
b = -2
end
if diverges() == true then
-- if the point does not diverge, then we add it to
-- the table with a key greater than the previous key by 1
key = key + 1
points[key] = {a = a,b = b}
end
end
end
fill(3, 0, 38, 255)
rect((WIDTH/2)-(canX*2),(HEIGHT/2)-(canY*2),canX*4,canY*4)
fill(89, 255, 0, 255)
for k,v in pairs(points) do
-- this draws all the points
pushStyle()
noSmooth()
if shape == "point" then
point((WIDTH/2)+(v.a*canX),(HEIGHT/2)+(v.b*canY))
end
if shape == "rect" then
rect((WIDTH/2)+(v.a*canX),(HEIGHT/2)+(v.b*canY),canX*res,canY*res)
end
if shape == "circle" then
ellipse((WIDTH/2)+(v.a*canX),(HEIGHT/2)+(v.b*canY),canX*res,canY*res)
end
smooth()
popStyle()
end

-- below are safe guards from Nan and inf values
-- I would like them to round these numbers instead of
-- setting them to 0.
-- Codeas values dont change/get stuck when they have the value of Nan or inf
if x ~= x then
x = 0
end
if y ~= y then
y = 0
end
-- below certain variables are printed so I can view them live
text(x.." "..y,WIDTH/2,HEIGHT-20)
text(a.." "..b,WIDTH/2,HEIGHT-40)
text(tostring(diverges()).." "..key,WIDTH/2,HEIGHT-60)
end
``````

Code stops

Cool right? Anyway, the reason behind all this is that I am trying to get the Mandelbrot formula right. You can copy/paste this if you want to check it out • Posts: 7,834

@PlatniumFrog Anytime you want to post code, put 3 ~'s on a line before and after the code so it formats correctly. I added them to your code above. There is a Mandelbrot example included with Codea. You can look at it for the formula.

• edited August 2016 Posts: 13

I knew that, but I thought that it just edited the sprite/icon. Am I wrong?

• edited August 2016 Posts: 7,834

The Mandelbrot example creates the Mandelbrot image. You can change the limit of the Mandelbrot calculations. I have some code for Mandelbrot that allows you to change the limit and also zoom in on selected areas.

• Posts: 7,834

@PlatniumFrog See this link for a better Codea Mandelbrot program.

``````https://codea.io/talk/discussion/2213/mandelbrot-essl-an-experiment-with-fragment-shaders-codea-1-5
``````