Nan value is stuck

PlatniumFrog

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?

dave1707

@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

Ignatz

If you still have problems, post the code

PlatniumFrog

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

dave1707

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

PlatniumFrog

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

dave1707

@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.

PlatniumFrog

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

dave1707

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.

dave1707

@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