I have a matrix defined mxn 128x128. And I have translated my 2d x,y positions onto this 1D matrix grid. My 2d coordinates accept positions using numbers 0->127 i.e. any combo in ranges {x=0,y=0}-->{x=127,y=127}. I'm implementing algorithms that take the neighboring positions of these nodes. Specifically the 8 surrounding positions of distance i (lets say i=1). So considering node={0,0}, my neighbours are generated by adding these vectors to said node:
two_d_nodes={
{0,i*1},{0,-i*1},{-i*1,0},{i*1,0},
{i*1,i*1},{i*1,-i*1},{-i*1,-i*1},{-i*1,i*1}
}
In terms of 2d though I am excluding neighbours outside the boundary. So in the above for node={0,0}, only neighours {0,1},{1,1}{1,0} are generated. Setting the boundary is basically just implementing some form of:
if x>=0 and y>=0 and x<=127 and y<=127 then...
The 1d translation of node={0,0} is node={0} and my vector additions translated to 1d are:
one_d_nodes={{128},{-128},{-1},{1},{129},{-127},{-129},{127}}
However the relationship with the 2d boundary expressions doesn't hold true here. Or at least I don't know how to translate it. In response I tried generating all the loose cases of the grid:
{0,127,16256,16383} --the 4 corner positions
node%128==0 --right-side boundary
node%128==1 --left-side boundary
node>1 and node<128 --top-side boundary
node>127*128 and node<128*128 --bottom-side boundary
Then tried implementing special cases....where I just ignored generating the specific out of bounds neighbours. That was messy, and didn't even work for some reason. Regardless I feel I am missing a much cleaner method.
So my question is: How do I translate my 2d boundaries onto my 1d grid for the purposes of only generating neighbours within the boundary?
The following is in regards to the answer below:
function newmatrix(node) --node={x=0,y=0}
local matrix={}
add(matrix,{(node.y<<8)+node.x}) --matrix= {{0},...}
--lets say [1 2 3] is a width=3; height=1 matrix,
--then the above line maps my 2d coord to a matrix of width=256, height=128
matrix.height, matrix.width = #node,#node[1] --1,1
return matrix
end
function indexmatrix(matrix, r,c)
if r > 1 and r <= matrix.height and c > 1 and c <= matrix.width then
return matrix[matrix.width * r + c]
else
return false
end
end
function getneighbors(matrix, r, c)
local two_d_nodes={
{0,1},{0,-1},{-1,0},{1,0},
{1,1},{1,-1},{-1,-1},{-1,1}
}
local neighbors = {}
for index, node in ipairs(two_d_nodes) do
table.insert(neighbors, indexmatrix(matrix, r + node[1], c + node[2]))
end
return neighbors
end
--Usage:
m={x=0,y=0}
matrix=newmatrix(m) --{{0}}
--here's where I'm stuck, cause idk what r and c are
--normally I'd grab my neighbors next....
neighbors=getneighbors(matrix)
--then I have indexmatrix for...?
--my understanding is that I am using indexmatrix to
--check if the nieghbors are within the bounds or not, is that right?
--can you illustrate how it would work for my code here, it should
--toss out anything with x less then 0 and y less than 0. Same as in OP's ex
indexmatrix(matrix) ---not sure what to do here
Attempt 2 in regards to the comment sections below:
function indexmatrix(matrix, x ,y)
if x > 1 and x <= matrix['height'] and y > 1 and y <= matrix['width'] then
return matrix[matrix['width'] * x + y]
else
return false
end
end
function getneighbors(matrix, pos_x, pos_y)
local two_d_nodes={
{0,1},{0,-1},{-1,0},{1,0},
{1,1},{1,-1},{-1,-1},{-1,1}
}
local neighbors = {}
for _, node in ipairs(two_d_nodes) do
add(neighbors, indexmatrix(matrix, pos_x + node[1], pos_y + node[2]))
end
return neighbors
end
matrix={} --128 columns/width, 128 rows/height
for k=1,128 do
add(matrix,{}) ----add() is same as table.insert()
for i=1,128 do
matrix[k][i]=i
end
end
id_matrix={{}} --{ {1...16k}}
for j=1,128*128 do
id_matrix[1][j]=j
end
id_matrix.height, id_matrix.width = 128,128
position={x=0,y=0}
neighbors = getNeighbors(matrix, position.x, position.y)
Attempt 3: A working dumbed down version of the code given. Not what I wanted at all.
function indexmatrix(x,y)
if x>=0 and y>=0 and x<127 and y<127 then
return 128 * x + y
else
return false
end
end
function getneighbors(posx,posy)
local two_d_nodes={
{0,1},{0,-1},{-1,0},{1,0},
{1,1},{1,-1},{-1,-1},{-1,1}
}
local neighbors = {}
for _, node in pairs(two_d_nodes) do
add(neighbors, indexmatrix(posx+node[1], posy + node[2]))
end
return neighbors
end
pos={x=0,y=10}
neighbors = getneighbors(pos.x,pos.y)
Edit: The equation to map 2D coordinates to 1D, y = mx + z, is a function of two variables. It is not possible for a multivariable equation to have a single solution unless a system of equations is given that gets x or z in terms of the other variable. Because x and z are independent of one another, the short answer to the question is: no
Instead, the constraints on x and z must be used to ensure integrity of the 1D coordinates.
What follows is an example of how to work with a 1D array as if it were a 2D matrix.
Let's say we have a constructor that maps a 2D table to a 1D matrix
local function newMatrix(m) -- m is 128x128 Matrix
local Matrix = {}
--logic to map m to 1D array
-- ...
return Matrix -- Matrix is m 1x16384 Array
end
The numeric indices are reserved, but we can add non-numeric keys to store information about the matrix. Let's store the number of rows and columns as height and width. We can do this in the constructor
local function newMatrix(m)
local Matrix = {}
--logic to map to 1D array
-- ...
-- Store row and column info in the matrix
Matrix.height, Matrix.width = #m, #m[1] -- Not the best way
return Matrix
end
Although the matrix is now a 1x16384 array, we can create a function that allows us to interact with the 1D array like it's still a 2D matrix. This function will get the value of a position in the matrix, but we return false/nil if the indices are out of bounds.
To be clear, the formula to map 2D coordinates to a 1D coordinate for a matrix, and can be found here:
1D position = 2D.x * Matrix-Width + 2D.y
And here's what that function could look like:
local function indexMatrix(Matrix, r,c)
if r >= 1 and r <= Matrix.height and c >= 1 and c <= Matrix.width then
return Matrix[Matrix.width * r + c] -- the above formula
else
return false -- out of bounds
end
end
We can now index our Matrix with any bounds without fear of returning an incorrect element.
Finally, we can make a function to grab the neighbors given a 2D position. In this function, we add vectors to the given 2D position to get surrounding positions, and then index the matrix using the indexMatrix function. Because indexMatrix checks if a 2D position is within the bounds of the original Matrix (before it was converted), we only get neighbors that exist.
local function getNeighbors(Matrix, r, c) -- r,c = row, column (2D position)
local two_d_nodes={
{0,1},{0,-1},{-1,0},{1,0},
{1,1},{1,-1},{-1,-1},{-1,1}
}
local neighbors = {}
for index, node in ipairs(two_d_nodes) do
-- Add each vector to the given position and get the node from the Matrix
table.insert(neighbors, indexMatrix(Matrix, r + node[1], c + node[2]))
end
return neighbors
end
You can either skip elements that return false from indexMatrix or remove them after the fact. Or anything else that sounds better to you (this code is not great, it's just meant to be an example). Wrap it in a for i ... do loop and you can go out an arbitrary distance.
I hope I haven't assumed too much and that this is helpful. Just know it's not foolproof (the # operator stops counting at the first nil, for instance)
Edit: Usage
Matrix = {
{1,2,3...128}, -- row 1
{1,2,3...128},
...
{1,2,3...128}, -- row 128
}
Array = newMatrix(Matrix) -- Convert to 1D Array ({1,2,3,...,16384})
--Array.width = 128, Array.height = 128
position = {x=0, y=0}
neighbors = getNeighbors(Array, position.x, position.y)
-- neighbors is: {{0,1}, false, false, {1,0}, {1,1}, false, false, false}
I need Help adding a if clause to my Change Maker, so that if say I have denominations of coins that can't equal the input coin value. For Example I have Coins worth 2,4,6 and I have a Value of 1. I Want it to return Change Not Possible I tried adding a clause to it below but when I test it I get 1.#INF
I also am curious how I can find the optimal coin solution, So on top of saying the minimum number of coins it returns the optimal coin setup if there is one.
function ChangeMaking(D,n)
--[[
//Applies dynamic programming to find the minimum number of coins
//of denominations d1< d2 < . . . < dm where d1 = 1 that add up to a
//given amount n
//Input: Positive integer n and array D[1..m] of increasing positive
// integers indicating the coin denominations where D[1]= 1
//Output: The minimum number of coins that add up to n
]]
F = {} -- F is List Array of Coins
m = tablelength(D)
F[0] = 0
for i =1,n do
temp = math.huge
j = 1
while j <= m and i >= D[j] do
temp = math.min(F[ i - D[j] ], temp)
j = j + 1
end
F[i] = temp + 1
end
--I wanted to Catch the failed Solution here but I return 1.#INF instead
--if F[n] <= 0 and F[n] == 1.#INF then print("No Change Possible") return end
return F[n]
end
function main()
--[[
//Prints a Greeting, Asks for Denominations separated by spaces.
// Iterates through the input and assigns values to table
// Table is then input into ChangeMaker, and a while loop takes an n value for user input.
// User Enters 0 to end the Loop
]]
io.write("Hello Welcome the to Change Maker - LUA Edition\nEnter a series of change denominations, separated by spaces: ")
input = io.read()
deno = {}
for num in input:gmatch("%d+") do table.insert(deno,tonumber(num)) end
local i = 1
while i ~= 0 do
io.write("Please Enter Total for Change Maker, When Finished Enter 0 to Exit: ")
input2 = io.read("*n")
if input2 ~= 0 then io.write("\nMinimum # of Coins: " .. ChangeMaking(deno,input2).."\n") end
if input2 == 0 then i=0 print("0 Entered, Exiting Change Maker") end
end
end
function tablelength(T)
--[[
//Function for grabbing the total length of a table.
]]
local count = 0
for _ in pairs(T) do count = count + 1 end
return count
end
main()
I have written a program to print a matrix after some computations and I am getting an output of nan for all elements. I want to break a for loop as soon as the matrix's first element becomes nan to understand the problem. How can I do this? In the terminal, I have printed the matrix a containing nan as all elements and typed a[1][1]=="nan" and a[{{1},{1}}]=="nan" both of which return false. Why are they not returning false and what statement should I use instead?
Your test fails because you are comparing a number with a string, "nan".
If you are sure it's a number, the easiest way is:
if a[1][1] ~= a[1][1] then
because according to IEEE 754, a nan value is considered not equal to any value, including itself.
Two solutions:
local n = 0/0 -- nan
-- first solution
if ( tostring(n) == "nan" ) then
print("is nan!!")
end
-- second solution
if (n ~= n) then
print("is nan!!")
end
Try this:
for x = 1, x2 do -- x2 depends on how big you matrix is.
for y = 1, y2 do -- y2 the same as x2
-- some code depending on how your program works
if a[x][y] == nan then
print( "X:" .. x .. ", Y:" .. y )
break
end
end
end
PS: (nan == nan) is true
I'm new to lua and I have this assignment and one of the questions I'm really stumped on is asking:
"A program that asks the user repeatedly for students' scores, will stop when the user enters a score of 999 then the program should calculate and display the number of scores entered, highest score, lowest score, and the average score. Make sure to display an error message if a score less than zero or more than 100 is entered by user. "
I've been at this all week long and still can't figure out what to do and its due at 11:59pm est. Any insight and direction would be great.
-How do I input multiple values in a growing table scores = {}? Where the size is given by the number of inputs for variable s after the user enters 999 and ends the repeat loop. This is actually my BIGGEST problem.
My Code:
local scores = {}, avg
repeat
io.write("Enter score(s)")
local s = tonumber(io.read()) --input and convert data type
print(s, type(s)) --s value, check input type
if(s < 0 or s > 100) then
print("Error.")
end
until (s == 999)
for i = 0, #s, 1 do
sum = 0
if s then
sum = sum + s
end
end
-- -----------------------------------------------------------Attemps to find a way to put s values in scores table-----------------------------------------------------------------------------------------
--[[scores[#scores+1] = s ----Attempt 1
print (scores)
for i = 0, #s, 1 do ----Attempt 2
scores{s} = s[i]
print (i, scores) --tried a multitude of different ways and
--kept getting the same number printed once or memory location of last entered number
end
for i, s in ipairs (scores) do --Attempt 3
print (i, s)
end
for i = 0, #s, 1 do
sum = 0
if s then
sum = sum + s
end
end --]]
-- -----------------------------------------------------------------------------------------------------------------------------------------------------------------------
--[[function average(myTable)
local sum = 0
for i in scores do
sum = sum + i
end
return (sum / #scores)
end
print ("The number of values in the table"..#scores)
print ("The average of the scores is "..average(s))
print ("The max value in the table is "..math.max(s))
print ("The minimum value in the table is "..math.min(s))
table.maxn(scores), table.minn(scores)
--]]
io.write("Please press enter to continue")
io.read()
So, I have been working on this game for a bit. However, over the past day I have not been able to figure out how to work my collision detection.
The scale at default is equal to 2.
The player is 41*scale by 64*scale.
My player is centered in the middle of the screen in both the x and y axis.
Since the player is centered the world is what moves, those variables are worldx and worldy. The player always stays at the center of the screen.
My tile map is stored in an array and is based on the image pixel color. If the pixel is white at map[x][y] the value is set to 0 else it's set to the block. Meaning the block does not get rendered.
for x = 0, w-1 do --scans the image and builds the map array
amap[x] = {}
for y = 0, h-1 do
local r, g, b, a = source:getPixel(x, y)
if r == 255 and g == 255 and b == 255 then
block = 0
end
if r == 255 and g == 100 and b == 0 then
block = 1
end
if r == 130 and g == 125 and b == 0 then
block = 2
end
if r == 76 and g == 76 and b == 76 then
block = 3
end
if r == 255 and g == 0 and b == 255 then
--this is the spawn pixel yet to build
end
amap[x][y] = block
end
end --end function
function that draws the map
for x = 0, w-1 do --draws the map
for y = 0, h-1 do
if amap[x][y] ~= 0 then
love.graphics.drawq(ImgBlocks, Blocks[amap[x][y]], 32*x*(3/bscale) + worldx, 32*y*(3/bscale) + worldy + jy, 0 , 3/bscale, 3/bscale)
end
if amap[x][y] == 4 then
end
end
end --end function
The function needs to return true or false base on if there is collision between player and block.
Your tiles are 32x32, correct? (from the drawq call) I would recommend you make a function that checks if a point is in a solid tile:
function pointCollisionTest(x, y)
-- find which tile the point is in
local tx, ty = math.floor(x / 32), math.floor(y / 32)
-- check the tile
if map[tx][ty] == solid then
return true
else
return false
end
end
You'll have to change the if map[x][y] == solid logic based on how you determine solid tiles, but this code should otherwise work.
Once you have point collision, the way you make the player collide is by checking each corner of its hitbox (which you should easily be able to determine) against this function whenever the player moves. There are a few ways to do this; I use the relatively simple method of calculating the player's new position, testing it, then canceling the move entirely if the collision test returns true. You have to check/cancel the x and y components of the move separately, though, so the player can move along walls instead of sticking to them.
Are you asking for a basic 2d collision detection?
A simplified formula:
if (playerx > blockminx) and (playery < blockmaxx) and (playery > blockminy) and (playery < blockmaxy) then collission