lua - How can I correct an unwanted fisheye effect when drawing a scene with raycasting?

Hello I have a game using raycasting for the TI Nspire in Lua, and when the player faces a wall so that their degree they are facing is perpendicular to the length of the wall, I am having what is described as the fishbowl/fisheye effect.

How can I fix this? I have already looked here, and none of that makes sense to me. Here is my code:

map = {{0, 0, 50, 0},{50, 0, 50, 50},{50, 50, 0, 50},{0, 50, 0, 0}}

facing = 45 --"player rotation"

rays = {}
x, y = 25, 25

function raycast()
    for i,v in pairs(rays) do
        rays[i] = nil
    end

    rayf = facing + 30


    for i = 1, 320, 1 do --64, 5
        x_ray, y_ray = x, y
        ray()
        table.insert(rays, radius)
        rayf = rayf - (60/320)
    end
    platform.window:invalidate()
end

function ray()

    radius = 1
    for n = 1, 50, 1 do -- increase of testdot
        x_ray = math.floor(x + (radius * math.cos(rayf * 3.141592653/180)))
        y_ray = math.floor(y - (radius * math.sin(rayf * 3.141592653/180)))
        for k,v in pairs(map) do
            if (
                math.min(v[1],v[3]) <= x_ray and x_ray <= math.max(v[1],v[3])
            ) and (
                math.min(v[2],v[4]) <= y_ray and y_ray <= math.max(v[2],v[4])
            ) then

                --print("Collision")
                return true
            end
        end
        radius = n
    end
end

function on.paint(gc)
    gc:setColorRGB(0,200,255)

    gc:fillRect(0, 0, 320, 108)
    gc:setColorRGB(100,100,100)
    gc:fillRect(0, 109, 320, 109)
    gc:setColorRGB(100,0,100)
    for i,v in ipairs(rays) do
        gc:drawLine(i, 108.5 - ((100/v * 20)/2), i, 108.5 + ((100/v * 20)/2))
    end
end

function on.arrowKey(key)

    if key == 'left' then
        facing = facing + 3
    elseif key == 'right' then
        facing = facing - 3
    end
    if key == 'up' then
        y = y - 1
    elseif key == 'down' then
        y = y + 1
    end

    raycast()
end

I have also tried it like this:

map = {{0, 0, 50, 0},{50, 0, 50, 50},{50, 50, 0, 50},{0, 50, 0, 0}}

facing = 45 --"player rotation"
rays = {}
x, y = 25, 25


function raycast()
    for i,v in pairs(rays) do
        rays[i] = nil
    end

    rayf = facing + 30

    for i = 1, 320, 1 do --64, 5
        x_ray, y_ray = x, y
        ray()

        ----------------
        fisheyeradius = radius / (math.cos(rayf - facing))
        table.insert(rays, fisheyeradius)
        ----------------
        rayf = rayf - (60/320)
    end
    platform.window:invalidate()
end

function ray()

    radius = 1
    for n = 1, 50, 1 do -- increase of testdot
        x_ray = math.floor(x + (radius * math.cos(rayf * 3.141592653/180)))
        y_ray = math.floor(y - (radius * math.sin(rayf * 3.141592653/180)))
        for k,v in pairs(map) do
            if (
                math.min(v[1],v[3]) <= x_ray and x_ray <= math.max(v[1],v[3])
            ) and (
                math.min(v[2],v[4]) <= y_ray and y_ray <= math.max(v[2],v[4])
            ) then

                --print("Collision")
                return true
            end
        end
        radius = n
    end
end

function on.paint(gc)
    gc:setColorRGB(0,200,255)

    gc:fillRect(0, 0, 320, 106)
    gc:setColorRGB(100,100,100)
    gc:fillRect(0, 106, 320, 106)
    gc:setColorRGB(100,0,100)
    for i,v in ipairs(rays) do
        gc:drawLine(i, 108.5 - ((100/v * 20)/2), i, 108.5 + ((100/v * 20)/2))
    end
end

function on.arrowKey(key)

    if key == 'left' then
        facing = facing + 3
    elseif key == 'right' then
        facing = facing - 3
    end
    if key == 'up' then
        y = y - 1
    elseif key == 'down' then
        y = y + 1
    end

    raycast()
end

The wall originally looked like this:

But I have made changes around the ---------------, and now the wall looks like this:

I this supposed to occur?

Answer

I actually had to solve this some time ago. The easiest fix is to simply divide by cos(angle of ray - viewAngle) and use that as the distance