How does one override a function that was defined in a parent script?
Here's my parent script:
# Object.gd
extends Area2D
var id = 0
var coords
func _ready():
assign_values()
func assign_values():
var a = global_position.x
var b = global_position.y
#cantor pairing function
id = (a + b) * ( a + b + 1) / 2 + b
coords = global_position
Here's the script that extends the parent script. I am trying to overwrite the assign_values() function in the new script to calculate the id differently. When I call assign_values in the extended script the weirdest thing happens. I can't print the individual components of the coords vector anymore, even though the type checks out and printing the vector works fine, too.
# Road.gd
extends "res://Object.gd"
func assign_values():
coords = Vector2(128, 96)
var a = coords.x # <- Here be Dragons
var b = coords.y
#cantor pairing function
id = (a + b) * ( a + b + 1) / 2 + b
print(typeof(coords)) # prints 5 -> Vector2 type
print(coords) # prints (128, 96), looks alright
print(coords.x) # Boom! crashes with error Invalid get index 'x' (on base: 'Nil').
I'm at a loss why I get this weird vector error. Notably, the whole thing works if I just write a new function in the extended script, func assign_new_values(), but I am not sure this is the right way to do this. I expected Godot to override functions from parent scripts if they are just declared again, but that does not seem to work. What is the proper way to do this? Could not find anything in the documentation..
Related
I have three functions and i want two variables to run through all the functions. I tried doing this:
R = rot(mir(sca(P(1,:),P(2,:))));
however i get this error:
Error using mir (line 2)
Not enough input arguments.
Any suggestions?
%rot.m
function rot = rot(x,y)
rot = [ cos(pi/6)*x-sin(pi/6)*y; sin(pi/6)*x+cos(pi/6)*y ];
%mir.m
function mir = mir(x,y)
mir = [x;(-y)];
%sca.m
function sca = sca(x,y)
sca = [2*x;2*y];
You should not be surprised about the error. Function mir expect two parameters (in fact, all of your functions expect that), but you provide only one. Mind you, a matrix is considered one parameter. You can do either of the following to correct the problem:
Redefine mir to accept one parameter and split it inside the function into two separate variables
Redefine sca to return two values:
function [outx, outy] = sca(x, y)
outx = 2 * x;
outy = 2 * y;
and then pass them to mir like so:
[scax, scay] = sca(x, y);
mir(scax, scay);
Obviously, the same needs to be done to function rot as well.
In MATLAB if you have more then one output argument you have to explicitly specify the output variables. By default function always returns one (the first) argument.
In your situation one choice can be to change definitions of your functions in such a way that they receive only one input argument as a matrix. For example:
%mir.m
function mir = mir(xy)
mir = [xy(1,:); -xy(2,:)];
or even easier in this case (you can simplify other functions as well):
function xy = mir(xy)
xy(2,:) = -xy(2,:);
I hope you got the idea.
Then you can run:
R = rot(mir(sca(P(1:2,:))));
If you cannot change your function definitions for some reason, you will have to split the one-line call to three function into 3 lines:
S = sca(P(1,:),P(2,:));
M = mir(S(1,:),S(2,:));
R = rot(M(1,:),M(2,:));
As a homework assignment, I'm writing a code that uses the bisection method to calculate the root of a function with one variable within a range. I created a user function that does the calculations, but one of the inputs of the function is supposed to be "fun" which is supposed to be set equal to the function.
Here is my code, before I go on:
function [ Ts ] = BisectionRoot( fun,a,b,TolMax )
%This function finds the value of Ts by finding the root of a given function within a given range to a given
%tolerance, using the Bisection Method.
Fa = fun(a);
Fb = fun(b);
if Fa * Fb > 0
disp('Error: The function has no roots in between the given bounds')
else
xNS = (a + b)/2;
toli = abs((b-a)/2);
FxNS = fun(xns);
if FxNS == 0
Ts = xNS;
break
end
if toli , TolMax
Ts = xNS;
break
end
if fun(a) * FxNS < 0
b = xNS;
else
a = xNS;
end
end
Ts
end
The input arguments are defined by our teacher, so I can't mess with them. We're supposed to set those variables in the command window before running the function. That way, we can use the program later on for other things. (Even though I think fzero() can be used to do this)
My problem is that I'm not sure how to set fun to something, and then use that in a way that I can do fun(a) or fun(b). In our book they do something they call defining f(x) as an anonymous function. They do this for an example problem:
F = # (x) 8-4.5*(x-sin(x))
But when I try doing that, I get the error, Error: Unexpected MATLAB operator.
If you guys want to try running the program to test your solutions before posting (hopefully my program works!) you can use these variables from an example in the book:
fun = 8 - 4.5*(x - sin(x))
a = 2
b = 3
TolMax = .001
The answer the get in the book for using those is 2.430664.
I'm sure the answer to this is incredibly easy and straightforward, but for some reason, I can't find a way to do it! Thank you for your help.
To get you going, it looks like your example is missing some syntax. Instead of either of these (from your question):
fun = 8 - 4.5*(x - sin(x)) % Missing function handle declaration symbol "#"
F = # (x) 8-4.5*(x-sin9(x)) %Unless you have defined it, there is no function "sin9"
Use
fun = #(x) 8 - 4.5*(x - sin(x))
Then you would call your function like this:
fun = #(x) 8 - 4.5*(x - sin(x));
a = 2;
b = 3;
TolMax = .001;
root = BisectionRoot( fun,a,b,TolMax );
To debug (which you will need to do), use the debugger.
The command dbstop if error stops execution and opens the file at the point of the problem, letting you examine the variable values and function stack.
Clicking on the "-" marks in the editor creates a break point, forcing the function to pause execution at that point, again so that you can examine the contents. Note that you can step through the code line by line using the debug buttons at the top of the editor.
dbquit quits debug mode
dbclear all clears all break points
I'm new to Matlab and I'm trying to write custom function in matlab that would take function handle as one of its arguments.
I'm getting this error all the time:
Error using subsindex
Function 'subsindex' is not defined for values of class 'function_handle'.
Trying to debug I performed following test: I run command x = fminbnd(#humps, 0.3, 1). I proceeded as expected - I got result x = 0.6370.
So I created custom function called train and I copied ALL the code of function fminbnd to the file train.m. The only thing that I changed is the name, so that code of functions fminbnd and train is now identical except for the names.
Now I run both functions with the same argument and the custom function throws error while original fminbnd returns correct answer.
Here is the code:
>> x = fminbnd(#humps, 0.3, 1)
x =
0.6370
>> x = train(#humps, 0.3, 1)
Error using subsindex
Function 'subsindex' is not defined for values of class 'function_handle'.
Here is header of function train (everything else is copied from fminbnd):
function [xf,fval,exitflag,output] = train(funfcn,ax,bx,options,varargin)
Where is the problem?
Doing a which train showed me that there is a function in the neural network toolbox of the same name.
/Applications/MATLAB_R2009b.app/toolbox/nnet/nnet/#network/train.m % network method
You may be running the nnet train.m rather than the one you think you're running. Are you in the directory containing your train.m? When I made sure I was in the right directory, I got it to work:
>> which train
/Users/myuserid/train.m
>> x = train(#humps,0.3,1)
x =
0.6370
Maybe you can name your file something else like myfminbnd.m instead?
Instead of duplicating the whole fminbnd function, try:
function varargout = myfminbnd(varargin)
varargout = cell(1,nargout(#fminbnd));
[varargout{:}] = fminbnd(varargin{:});
end
this will work as an "alias" to the existing function:
>> fminbnd(#(x)x.^3-2*x-5, 0, 2)
ans =
0.8165
>> myfminbnd(#(x)x.^3-2*x-5, 0, 2)
ans =
0.8165
(you can get the other output arguments as well)
So I am trying to take a bit of code that I use for interactive selection and identification. It works outside of a function but gives an error when I try to run it as a stand alone function.
my.identify <- function(data)
{
# allows you to create a polygon by clicking on map
region = locator(type = "o")
n = length(region$x)
p = Polygon(cbind(region$x, region$y)[c(1:n,1),])
ps = Polygons(list(p), ID="region")
sps = SpatialPolygons(list(ps))
# returns all data that overlaps new polygon sps
a=data[!is.na(overlay(data,sps)),] # here is the problem
return(a)
}
Basically it doesn't want to run the overlay function (function of the sp package). The error report is that I can't run the inherited functions??
Error in function (classes, fdef, mtable) : unable to find an
inherited method for function "overlay", for signature "matrix",
"SpatialPolygons"
Any ideas??? I'm new to function writing... so hopefully it will be easy.
This should work. overlay is deprecated and over should be used instead. The catch is that all objects should be Spatial*.
xy <- data.frame(x = runif(40, min = -200, max = 200),
y = runif(40, min = -200, max = 200))
plot(xy)
my.identify <- function(data) {
# allows you to create a polygon by clicking on map
region = locator(type = "o")
n = length(region$x)
p = Polygon(cbind(region$x, region$y)[c(1:n,1),])
ps = Polygons(list(p), ID="region")
sps = SpatialPolygons(list(ps))
# returns all data that overlaps new polygon sps
a=data[!is.na(over(SpatialPoints(data),sps)),]
return(a)
}
ident <- my.identify(xy)
points(ident, pch = 16)
You need to add a call to the package in your function:
my.identify <- function(data)
{
require('sp') ## Call to load the sp package for use in stand alone function
# allows you to create a polygon by clicking on map
region = locator(type = "o")
n = length(region$x)
p = Polygon(cbind(region$x, region$y)[c(1:n,1),])
ps = Polygons(list(p), ID="region")
sps = SpatialPolygons(list(ps))
# returns all data that overlaps new polygon sps
a=data[!is.na(overlay(data,sps)),]
return(a)
}
I'm using Scilab and I'm trying to make a function like the following:
function p = binary_search(myf,a,b)
The target is to make a binary_search to find such p that: myf(p) = 0 in [a,b].
I want to do something like this:
root = binary_search("x^3 - 10",1,2)
Where the first string is a definition of a function.
The only way I found is defining a function called x3:
function x = x3(p)
x = p^3 - 10;
endfunction
and then, inside binary_search, do something like:
fa = x3(a);
Any ideas?
Thank You!
If you have defined the function f(x) = x^3 - 10 , either using deff('y=f(x)','y=x^3-10') or the regular "function ... endfunction" syntax, then you can simply pass f as an argument: define
function r = binary_search(f,a,b)
% do the binary search here and store the result in r
endfunction
Then you can call
---> binary_search(f, 1, 2)
which works fine in SciLab.
In MATLAB/octave, the interpreter considers " f " as an equivalent for f(), i.e., it would execute the function f without arguments, which will result in an error "x undefined". To avoid this, you have to type an # in front of f:
---> binary_search( #f, 1, 2) %% in MATLAB/octave
Functions in Scilab can be passed as arguments to other functions. Therefore, if you have one function, f:
function y=f(x)
y = x^3 - 10
endfunction
you are free to pass that to another function,
root = binary_search("x^3 - 10",1,2)
deff is simply a way to quickly define a function- usually inline on the interpreter.
Alternatively, you can also pass an expression as a string to a function and have that evaluated using the evstr command:
function p = binary_search(expression, a, b)
evstr expression
//Rest of your code
endfunction
You would implement this on the interpreter thus:
expression = "a^3 - 10"
root = binary_search(expression, 1, 2)
I found a solution:
In the main window (the interpreter), I define the function like:
deff('[y] = square(x)','y=x^2')
Then, I call
bi(square,0,2)
In the function, I just do 'f(x)':
function [x] = bi(f,a,b)
fa = f(a);