Until now, I change req manually. The code works, including saving the result into a file.
But now I want to run the code for all possible values of req.
Without saving it into a file, the code works but obviously it overwrite the result.
That is why I put that line of code that saving the result by giving it a different name depending of the values of req. But this gives me error.
error:
error: sprintf: wrong type argument 'cell'
error: called from
testforloop at line 26 column 1
my code:
clear all;
clc;
for req = {"del_1", "del_2", "del_3"}
request = req;
if (strcmp(request, "del_1"))
tarr = 11;
# and a bunch of other variables
elseif (strcmp(request, "del_2"))
tarr = 22;
# and a bunch of other variables
elseif (strcmp(request, "del_3"))
tarr = 33;
# and a bunch of other variables
else
# do nothing
endif
#long calculation producing many variable including aa, bb, cc.
aa = 2 * tarr;
bb = 3 * tarr;
cc = 4 * tarr;
#collecting variables of interest: aa, bb, cc and save it to a file.
result_matrix = [aa bb cc];
dlmwrite (sprintf('file_result_%s.csv', request), result_matrix);
endfor
if I use ["del_1" "del_2" "del_3"], the error is
error: 'tarr' undefined near line 20 column 10
error: called from
testforloop at line 20 column 4
Inside the loop
for req = {"del_1", "del_2", "del_3"}
req gets as value each of the cells of the cell array, not the contents of the cells (weird design decision, IMO, but this is the way it works). Thus, req={"del_1"} in the first iteration. The string itself can then be obtained with req{1}. So all you need to change is:
request = req{1};
However, I would implement this differently, as so:
function myfunction(request, tarr)
% long calculation producing many variable including aa, bb, cc.
aa = 2 * tarr;
bb = 3 * tarr;
cc = 4 * tarr;
% collecting variables of interest: aa, bb, cc and save it to a file.
result_matrix = [aa bb cc];
dlmwrite (sprintf('file_result_%s.csv', request), result_matrix);
end
myfunction("del_1", 11)
myfunction("del_2", 22)
myfunction("del_3", 33)
I think this obtains a clearer view of what you're actually doing, the code is less complicated.
Note that in Octave, ["del_1" "del_2" "del_3"] evaluates to "del_1del_2del_3". That is, you concatenate the strings. In MATLAB this is not the case, but Octave doesn't know the string type, and uses " in the same way as ' to create char arrays.
Related
I had the task to code the following:
Take a list of integers and returns the value of these numbers added up, but only if they are odd.
Example input: [1,5,3,2]
Output: 9
I did the code below and it worked perfectly.
numbers = [1,5,3,2]
print(numbers)
add_up_the_odds = []
for number in numbers:
if number % 2 == 1:
add_up_the_odds.append(number)
print(add_up_the_odds)
print(sum(add_up_the_odds))
Then I tried to re-code it using function definition / return:
def add_up_the_odds(numbers):
odds = []
for number in range(1,len(numbers)):
if number % 2 == 1:
odds.append(number)
return odds
numbers = [1,5,3,2]
print (sum(odds))
But I couldn’t make it working, anybody can help with that?
Note: I'm going to assume Python 3.x
It looks like you're defining your function, but never calling it.
When the interpreter finishes going through your function definition, the function is now there for you to use - but it never actually executes until you tell it to.
Between the last two lines in your code, you need to call add_up_the_odds() on your numbers array, and assign the result to the odds variable.
i.e. odds = add_up_the_odds(numbers)
I am using Octave 4.0.0.
I define A{1, 1} = 'qwe', but when I check existence of A{1, 1}, as in
exist("A{1,1}")
or
exist("A{1,1}", "var")
it returns 0.
How can I check its existence?
To check if an array has element say 3, 5, you need to verify that the array has at least 3 rows and 5 columns:
all(size(A) >= [3, 5])
You can of course check if variable A exists at all before-hand, and also is a cell array. A complete solution might be something like
function b = is_element(name, varargin)
b = false;
if ~evalin(['exists("' name '")'], 'caller')
return;
end
if ~strcmp(evalin(['class(' name ')'], 'caller'), 'cell')
return;
end
if evalin(['ndim(' name ')'], 'caller') ~= nargin - 1
return;
end
b = all(evalin(['size(' name ')'], 'caller') >= cell2mat(varargin))
endfunction
This function accepts a variable name and the multi-dimensional index you are interested in. It returns 1 if the object exists as a cell array of sufficient dimensionality and size to contain the requested element.
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've been looking around and I have not been able to find anything that has worked for me. I'm starting to learn more Lua and to start off I'm making a simple calculator. I was able to get each individual operation onto separate programs, but when I try to combine them I just can't get it to work. My script as it is now is
require "io"
require "operations.lua"
do
print ("Please enter the first number in your problem.")
x = io.read()
print ("Please enter the second number in your problem.")
y = io.read()
print ("Please choose the operation you wish to perform.")
print ("Use 1 for addition, 2 for subtraction, 3 for multiplication, and 4 for division.")
op = io.read()
op = 1 then
function addition
op = 2 then
function subtraction
op = 3 then
function multiplication
op = 4 then
function division
print (answer)
io.read()
end
and my operations.lua script is
function addition
return answer = x+y
end
function subtraction
return answer = x-y
end
function multiplication
return answer = x*y
end
function division
return answer = x/y
end
I've tried using
if op = 1 then
answer = x+y
print(answer)
if op = 2 then
answer = x-y
print(answer)
and I did that completing each operation. But it doesn't work. I can't even get the error code that it's returning because it closes so fast. What should I do?
In your example, make these changes: You require operations.lua without the extension. Include parameters in your operations function definitions. Return the operation expression directly versus returning a statement like answer = x+y.
All together:
Code for operations.lua
function addition(x,y)
return x + y
end
--more functions go here...
function division(x,y)
return x / y
end
Code for your hosting Lua script:
require "operations"
result = addition(5,7)
print(result)
result = division(9,3)
print(result)
Once you get that working, try re-adding your io logic.
Keep in mind that as it's coded, your functions will be defined globally. To avoid polluting the global table, consider defining operations.lua as a module. Take a look at the lua-users.org Modules Tutorial.
The right if-then-else syntax:
if op==1 then
answer = a+b
elseif op==2 then
answer = a*b
end
print(answer)
After: please check the correct function-declaration syntax.
After: return answer=x+y is incorrect. If you want set answer's value, set without return. If you want return the sum, please use return x+y.
And I think you should check Programming in Lua.
First of all, learn to use the command line so you can see the errors (on Windows that would be cmd.exe).
Second, change the second line to require("operations"). The way you did it the interpreter expects a directory operations with an underlying script lua.lua.
I'm new to Lua, so (naturally) I got stuck at the first thing I tried to program. I'm working with an example script provided with the Corona Developer package. Here's a simplified version of the function (irrelevant material removed) I'm trying to call:
function new( imageSet, slideBackground, top, bottom )
function g:jumpToImage(num)
print(num)
local i = 0
print("jumpToImage")
print("#images", #images)
for i = 1, #images do
if i < num then
images[i].x = -screenW*.5;
elseif i > num then
images[i].x = screenW*1.5 + pad
else
images[i].x = screenW*.5 - pad
end
end
imgNum = num
initImage(imgNum)
end
end
If I try to call that function like this:
local test = slideView.new( myImages )
test.jumpToImage(2)
I get this error:
attempt to compare number with nil
at line 225. It would seem that "num" is not getting passed into the function. Why is this?
Where are you declaring g? You're adding a method to g, which doesn't exist (as a local). Then you're never returning g either. But most likely those were just copying errors or something. The real error is probably the notation that you're using to call test:jumpToImage.
You declare g:jumpToImage(num). That colon there means that the first argument should be treated as self. So really, your function is g.jumpToImage(self, num)
Later, you call it as test.jumpToImage(2). That makes the actual arguments of self be 2 and num be nil. What you want to do is test:jumpToImage(2). The colon there makes the expression expand to test.jumpToImage(test, 2)
Take a look at this page for an explanation of Lua's : syntax.