i have the following error in my matlab function code:
??? Subscript indices must either be real positive integers or logicals.
Error in ==> AFA at 15
M(k,j) = mean(T(i:sze,j));
here is the part of the code where the problem is :
sz =size(T);
lim = sz(2) - ordre;
M = zeros(sz(1),sz(2));
r= 0;
for j=1:sze,
k = 1;
for i=1:lim,
M(k,j) = mean(T(i:i+ordre,j));
k = k + 1;
end
for i=lim+1:sz(2),
M(k,j) = mean(T(i:sz(2),j));
k = k + 1;
end
end
The following works for me without error
T = magic(25);ordre = 5; %# I make up some values here
sz =size(T);
lim = sz(2) - ordre;
%# I've added a check here
if lim < 1, error('ordre has to be at most sz(2)-1 (is %i)',ordre);end
M = zeros(sz(1),sz(2));
r= 0;
for j=1:sz(2), %# I needed to change this line (sz(1) works as well)
k = 1;
for i=1:lim,
M(k,j) = mean(T(i:i+ordre,j));
k = k + 1;
end
for i=lim+1:sz(2),
M(k,j) = mean(T(i:sz(2),j));
k = k + 1;
end
end
Related
I want to determine the Steepest descent of the Rosenbruck function using Armijo steplength where x = [-1.2, 1]' (the initial column vector).
The problem is, that the code has been running for a long time. I think there will be an infinite loop created here. But I could not understand where the problem was.
Could anyone help me?
n=input('enter the number of variables n ');
% Armijo stepsize rule parameters
x = [-1.2 1]';
s = 10;
m = 0;
sigma = .1;
beta = .5;
obj=func(x);
g=grad(x);
k_max = 10^5;
k=0; % k = # iterations
nf=1; % nf = # function eval.
x_new = zeros([],1) ; % empty vector which can be filled if length is not known ;
[X,Y]=meshgrid(-2:0.5:2);
fx = 100*(X.^2 - Y).^2 + (X-1).^2;
contour(X, Y, fx, 20)
while (norm(g)>10^(-3)) && (k<k_max)
d = -g./abs(g); % steepest descent direction
s = 1;
newobj = func(x + beta.^m*s*d);
m = m+1;
if obj > newobj - (sigma*beta.^m*s*g'*d)
t = beta^m *s;
x = x + t*d;
m_new = m;
newobj = func(x + t*d);
nf = nf+1;
else
m = m+1;
end
obj=newobj;
g=grad(x);
k = k + 1;
x_new = [x_new, x];
end
% Output x and k
x_new, k, nf
fprintf('Optimal Solution x = [%f, %f]\n', x(1), x(2))
plot(x_new)
function y = func(x)
y = 100*(x(1)^2 - x(2))^2 + (x(1)-1)^2;
end
function y = grad(x)
y(1) = 100*(2*(x(1)^2-x(2))*2*x(1)) + 2*(x(1)-1);
end
I want the function P to look like this:
-1 + 0.6366*(x+pi/2) + (-0.000)*(x + pi/2)*(x)
and right now it looks like this
(5734161139222659*x)/9007199254740992 + (5734161139222659*pi)/18014398509481984 - (8131029572207409*x*(x + pi/2))/324518553658426726783156020576256 - 1.
How to convert S array so that the values are not symbolic?
syms P x
f = sin(x);
f = matlabFunction(f);
X = [-pi/2, 0, pi/2];
Y = f(sym(X));
P = MetN(X,Y,x)
P = matlabFunction(P);
function [P] = MetN(X,Y,x)
n = length(X);
for i = 1:n
A(i,1) = 1;
end
for i = 2:n
for j = 2: n
if i >= j
produs = 1;
for k =1:j-1
produs = produs * (X(i) - X(k));
end
A(i,j) = produs;
end
end
end
S = SubsAsc(A, Y);
S = double(S);
disp(S);
sym produs
P = double(sym(S(1)));
for i = 2:n
produs = 1;
for j = 1:i-1
produs = produs * (x - sym(X(j)));
end
disp(produs);
P = P + double(S(i))*produs;
end
end
function [x] = SubsAsc(A,b)
n = length(b);
x(1) = (1/A(1,1))*b(1);
for k = 2:n
s = 0;
for j = 1:k-1
s = s + A(k,j)*x(j);
end
x(k) = (1/A(k,k))*(b(k)-s);
end
end
The output you currently have is because symbolic uses exact arithmetic, so it outputs it as a rational number (hence the ugly fraction).
To have it output P using decimals, use vpa(). For instance output P using decimals to 5 significant digits
>> vpa(P, 5)
ans =
0.63662*x - 2.5056e-17*x*(x + 1.5708)
This will, however, also round pi, so you can't really have the best of both worlds here.
I'm trying to build make a code where an equation is not calculated for some certain values. I have a meshgrid with several values for x and y and I want to include a for loop that will calculate some values for most of the points in the meshgrid but I'm trying to include in that loop a condition that if the points have a specified index, the value will not be calculated. In my second group of for/if loops, I want to say that for all values of i and k (row and column), the value for z and phi are calculated with the exception of the specified i and k values (in the if loop). What I'm doing at the moment is not working...
The error I'm getting is:
The expression to the left of the equals sign is not a valid target for an assignment.
Here is my code at the moment. I'd really appreciate any advice on this! Thanks in advance
U_i = 20;
a = 4;
c = -a*5;
b = a*10;
d = -20;
e = 20;
n = a*10;
[x,y] = meshgrid([c:(b-c)/n:b],[d:(e-d)/n:e]');
for i = 1:length(x)
for k = 1:length(x)
% Zeroing values where cylinder is
if sqrt(x(i,k).^2 + y(i,k).^2) < a
x(i,k) = 0;
y(i,k) = 0;
end
end
end
r = sqrt(x.^2 + y.^2);
theta = atan2(y,x);
z = zeros(length(x));
phi = zeros(length(x));
for i = 1:length(x)
for k = 1:length(x)
if (i > 16 && i < 24 && k > 16 && k <= length(x))
z = 0;
phi = 0;
else
z = U_i.*r.*(1-a^2./r.^2).*sin(theta); % Stream function
phi = U_i*r.*(1+a^2./r.^2).*cos(theta); % Velocity potential
end
end
end
The original code in the question can be rewritten as seen below. Pay attention in the line with ind(17:24,:) since your edit now excludes 24 and you original question included 24.
U_i = 20;
a = 4;
c = -a*5;
b = a*10;
d = -20;
e = 20;
n = a*10;
[x,y] = meshgrid([c:(b-c)/n:b],[d:(e-d)/n:e]');
ind = find(sqrt(x.^2 + y.^2) < a);
x(ind) = 0;
y(ind) = 0;
r = sqrt(x.^2 + y.^2);
theta = atan2(y,x);
ind = true(size(x));
ind(17:24,17:length(x)) = false;
z = zeros(size(x));
phi = zeros(size(x));
z(ind) = U_i.*r(ind).*(1-a^2./r(ind).^2).*sin(theta(ind)); % Stream function
phi(ind) = U_i.*r(ind).*(1+a^2./r(ind).^2).*cos(theta(ind)); % Velocity potential
I'm trying to write my own program to sort vectors in matlab. I know you can use the sort(A) on a vector, but I'm trying to code this on my own. My goal is to also sort it in the fewest amount of swaps which is kept track of by the ctr variable. I find and sort the min and max elements first, and then have a loop that looks at the ii minimum vector value and swaps it accordingly.
This is where I start to run into problems, I'm trying to remove all the ii minimum values from my starting vector but I'm not sure how to use the ~= on a vector. Is there a way do this this with a loop? Thanks!
clc;
a = [8 9 13 3 2 8 74 3 1] %random vector, will be function a once I get this to work
[one, len] = size(a);
[mx, posmx] = max(a);
ctr = 0; %counter set to zero to start
%setting min and max at first and last elements
if a(1,len) ~= mx
b = mx;
c = a(1,len);
a(1,len) = b;
a(1,posmx) = c;
ctr = ctr + 1;
end
[mn, posmn] = min(a);
if a(1,1) ~= mn
b = mn;
c = a(1,1);
a(1,1) = b;
a(1,posmn) = c;
ctr = ctr + 1;
end
ii = 2; %starting at 2 since first element already sorted
mini = [mn];
posmini = [];
while a(1,ii) < mx
[mini(ii), posmini(ii - 1)] = min(a(a~=mini))
if a(1,ii) ~= mini(ii)
b = mini(ii)
c = a(1,ii)
a(1,ii) = b
a(1,ii) = c
ctr = ctr + 1;
end
ii = ii + 1;
end
I have the following error in MATLAB:
??? Subscript indices must either be real positive integers or
logicals.
Error in ==> Lloyd_Max at 74 D(w_count) = mean((x -
centers(xq)).^2);
This is my code :
function [ xq,centers,D ] = Lloyd_Max( x,N,min_value,max_value )
%LLOYD_MAX Summary of this function goes here
% Detailed explanation goes here
x = x';
temp = (max_value - min_value)/2^N;
count=1;
for j=0:temp:((max_value - min_value)-temp),
centers(count) = (j + j + temp )/2;
count = count + 1;
end
for i=1:length(centers),
k(i) = centers(i);
end
w_count = 0;
while((w_count < 2) || (D(w_count) - D(w_count - 1) > 1e-6))
w_count = w_count + 1;
count1 = 2;
for i=2:(count-1),
T(i) = (k(i-1) + k(i))/2;
count1 = count1 +1 ;
end
T(1) = min_value;
T(count1) = max_value;
index = 1;
for j=2:count1,
tempc = 0;
tempk = 0;
for k=1:10000,
if(x(k) >= T(j-1) && x(k) < T(j))
tempk = tempk + x(k);
tempc = tempc + 1;
end
end
k(index) = tempk;
k_count(index) = tempc;
index = index + 1;
end
for i=1:length(k),
k(i) = k(i)/k_count(i);
end
for i=1:10000,
if (x(i) > max_value)
xq(i) = max_value;
elseif (x(i) < min_value)
xq(i) = min_value;
else
xq(i) = x(i);
end
end
for i=1:10000,
cnt = 1;
for l=2:count1,
if(xq(i) > T(l-1) && xq(i) <= T(l))
xq(i) = cnt;
end
cnt = cnt +1 ;
end
end
D(w_count) = mean((x - centers(xq)).^2);
end
end
and i call it and have these inputs :
M = 10000
t=(randn(M,1)+sqrt(-1)*randn(M,1))./sqrt(2);
A= abs(t).^2;
[xq,centers,D] = Lloyd_Max( A,2,0,4 );
I tried to comment the while and the D, Results :
I got the xq and the centers all normal, xq in the 1-4 range, centers 1-4 indexes and 0.5-3.5 range.
I dont know whats going wrong here...Please help me.
Thank in advance!
MYSTERY SOVLED!
Thank you all guys for your help!
I just putted out of the while the for loop :
for i=1:10000,
if (x(i) > max_value)
xq(i) = max_value;
elseif (x(i) < min_value)
xq(i) = min_value;
else
xq(i) = x(i);
end
end
and it worked like charm.... this loop was initilizing the array again. Sorry for that. Thank you again!
There is an assignment xq(i) = x(i) somewhere in the middle of your function, but you pass A as x from outside where you calculate A from t which is sampled by randn, so you can't promise xq is an integer.
I'm not sure exactly what you are aiming to do, but your vector xq does not contain integers, it contains doubles. If you want to use a vector of indices as you do with centers(xq), all elements of the vector need to be integers.
Upon a little inspection, it looks like xq are x values, you should find some way to map them to the integer of the closest cell to which they belong (i'm guessing 'centers' represents centers of cells?)