I need to multiply some values bys using this line of code:
% Apply hypothetical keys
tmp = bitxor( Y_i*ones(1,length(K)) , ones(length(Y_i),1)*K );
The error that I found is:
error: binary operator `*' not implemented for `int32 matrix' by `matrix' operations
error: evaluating binary operator `*' near line 49, column 17
error: evaluating argument list element number 1
error: evaluating assignment expression near line 49, column 7
Related
here is my problem. I'm trying to solve a system of two differential equations thanks to the two functions below. The part of the code that give me some trouble is the variable "rho". "rho" is a function which values are given from a file and that I tried to put in the the variable rho.
function [xdot]=f2(x,t)
# Parameters of the equations
t=[1:1:35926];
x = dlmread('data_txt.txt');
rho=x(:,4);
beta = 0.68*10^-2;
g = 1.5;
l = 1.6;
# Definition of the system of 2 ODE's :
xdot(1) = ((rho-beta)/g)*x(1) + l*x(2);
xdot(2) = (beta/g)*x(1)-l*x(2);
endfunction
.
# Initial conditions for the two variables :
x0 = [0;1];
# Definition of the time-vector -> (initial time,temporal mesh,final time) :
t = linspace (1, 10, 10000);
# Resolution with the lsode routine :
x = lsode ("f2", x0, t);
# Plot of the two curves :
plot (t,x);
When I run my code, I get the following error:
>> resolution_effective2
error: f2: A(I) = X: X must have the same size as I
error: called from
f2 at line 34 column 9
resolution_effective2 at line 8 column 3
error: lsode: evaluation of user-supplied function failed
error: called from
resolution_effective2 at line 8 column 3
error: lsode: inconsistent sizes for state and derivative vectors
error: called from
resolution_effective2 at line 8 column 3
I know that my error comes from a mismatch of size between some variable but I have been looking for the error for days now and I don't see. Could someone try to give and explain me an effective correction ?
Thank you
The error might come from your function f2. Its first argument x should have the same dimension as x0 since x0 is the initial condition of x.
In your case, whatever you intent to be the first argument of f2 is ignored since in your function you do x = dlmread('data_txt.txt'); this seems to be a mistake.
Then, xdot(1) = ((rho-beta)/g)*x(1) + l*x(2); will be a problem since rho is a vector.
You need to check the dimensions of x and rho.
Have a file called f.m which has the following:
function xdot = f (x,t)
xdot = -exp(-t)*x^2;
endfunction
x=lsode("f",2,(t=linspace(0,5,50)'));
plot(t,x)
Running in octave 4.2.2 or 4.2.1 produces the following error:
error: 't' undefined near line 2 column 14
error: called from
f at line 2 column 6
I have the following function definition:
create or replace FUNCTION checkXML
(idx in number(19))
return number(19)
is
...
But when I compile it, am getting the following errors,
Error(2,16): PLS-00103: Encountered the symbol "(" when expecting one of the
following: := . ) , # % default character The symbol ":=" was substituted for
"(" to continue.
Error(3,15): PLS-00103: Encountered the symbol "(" when expecting one of the
following: . # % ; is authid as cluster order using external character
deterministic parallel_enable pipelined aggregate result_cache
Change the function declaraction to be
create or replace FUNCTION checkXML
(idx in number)
return number
PL/SQL doesn't accept length or precision specifiers on parameters or return types.
Share and enjoy.
I tried to make a summation list in Sage. The commands were:
sage: var('n')
sage: var('x')
sage: f = (2/n)*(sin(n*x)*(-1)^(n+1))
sage: funclist = [sum(f,n,1,20) for n in range(1,3)]
but it was error:
TypeError: need a summation variable
but when i tried some similar things on python shell. There was no any problem.
>>> x=1
>>> [pow(x,2) for x in range(1,9)]
[1, 4, 9, 16, 25, 36, 49, 64]
and return to Sage, there was no problem if i run program on Sage like this:
sage: var('n')
sage: var('x')
sage: sum(f,n,1,20)
-1/2*sin(4*x) + 2/3*sin(3*x) - sin(2*x) + 2*sin(x)
I don't know how Sage combine a 'sum' function into its program. And don't know how to solve this problem.
Sage shell is different from the Pytyhon shell, and the function sum is different too. In Sage, it tries to find a symbolic sum, that's why the second argument needs to be a variable. In your first code block, you are essentially trying to evaluate
[sum(f, 1, 1, 20), sum(f, 2, 1, 20)]
From the mathematical point of view, how do you sum over 1? That's why Sage gives you an error. Notice that in the last code block, when you use the variable n, Sage is able to calculate the sum.
So I have the function integral(function, n=1000, start=0, stop=100) defined in nums.py:
def integral(function, n=1000, start=0, stop=100):
"""Returns integral of function from start to stop with 'n' rectangles"""
increment, num, x = float(stop - start) / n, 0, start
while x <= stop:
num += eval(function)
if x >= stop: break
x += increment
return increment * num
However, my teacher (for my Programming class) wants us to create a separate program that gets the input using input() and then returns it. So, I have:
def main():
from nums import integral # imports the function that I made in my own 'nums' module
f, n, a, b = get_input()
result = integral(f, n, a, b)
msg = "\nIntegration of " + f + " is: " + str(result)
print(msg)
def get_input():
f = str(input("Function (in quotes, eg: 'x^2'; use 'x' as the variable): ")).replace('^', '**')
# The above makes it Python-evaluable and also gets the input in one line
n = int(input("Numbers of Rectangles (enter as an integer, eg: 1000): "))
a = int(input("Start-Point (enter as an integer, eg: 0): "))
b = int(input("End-Point (enter as an integer, eg: 100): "))
return f, n, a, b
main()
When run in Python 2.7, it works fine:
>>>
Function (in quotes, eg: 'x^2'; use 'x' as the variable): 'x**2'
Numbers of Rectangles (enter as an integer, eg: 1000): 1000
Start-Point (enter as an integer, eg: 0): 0
End-Point (enter as an integer, eg: 100): 100
Integration of x**2 is: 333833.5
However, in Python 3.3 (which my teacher insists we use), it raises an error in my integral function, with the same exact input:
Traceback (most recent call last):
File "D:\my_stuff\Google Drive\documents\SCHOOL\Programming\Python\Programming Class\integration.py", line 20, in <module>
main()
File "D:\my_stuff\Google Drive\documents\SCHOOL\Programming\Python\Programming Class\integration.py", line 8, in main
result = integral(f, n, a, b)
File "D:\my_stuff\Google Drive\Modules\nums.py", line 142, in integral
num += eval(function)
TypeError: unsupported operand type(s) for +=: 'int' and 'str'
In addition, integral by itself (in Python 3.3) works fine:
>>> from nums import integral
>>> integral('x**2')
333833.4999999991
Because of that, I believe the fault is in my program for my class... Any and all help is appreciated. Thanks :)
The issue you're running into is that input works differently in Python 2 and Python 3. In Python 3, the input function works like the raw_input does in Python 2. Python 2's input function is equivalent to eval(input()) in Python 3.
You're getting into trouble because of the quoteation marks you're typing with the formula. When you type 'x**2' (with the quotes) as your formula when running on Python 2, the text gets evaled in the input function and you get a string with no quotation marks as the result. This works.
When you give the same string to Python 3's input function, it doesn't do an eval, so the quotation marks remain. When you later eval the formula as part of your integral calculation, you get the string x**2 (without any quotation marks) as the result, not the value of x squared. This results in an exception when you try the string to 0.
To fix this, I suggest either using just one version of Python, or putting the following code at the top of your file to get a Python 3 style input in both versions:
# ensure we have Python 3 semantics from input, even in Python 2
try:
input = raw_input
except NameError:
pass
Then just type in your formula without quotation marks and it should work correctly.