I'm having an issue where, for the first for loop I'm getting my desired output at no2_iterate(1) but within the second loop made to generate no2_iterate(2) I'm not getting any output whatsoever.
The following are my two if-statements/for loops to generate no2_iterate(1) & (2).
no2_sum_1cm = 0;
gridh_iterate = 0 % starting height in cm
lato = 1;
lono = 1;
no2_iterate_start = 0;
no2_iterate(1:2) = 0;
if gridh_iterate < gridh(lato,lono,1);
no2_layer = no2_moleccm3(lato,lono,1,12);
for i = 1:gridh(lato,lono,1);
for h = 1;
gridh_iterate = gridh_iterate+ 1; % in cm, now compare to gridh(1,1,1) and the other areas, so if its over the height of the cell switch no2 concn
end
no2_iterate(1) = (no2_iterate(1) + no2_layer)*1; % Now units of g no2/cm2
end
no2_iterate = no2_iterate
end
if gridh_iterate < gridh(lato,lono,2) && gridh_iterate >gridh(lato,lono,1);
no2_layer = no2_moleccm3(lato,lono,2,12);
for i = 1:gridh(lato,lono,2);
for h = 1;
gridh_iterate = gridh_iterate + 1; % in cm, now compare to gridh(1,1,1) and the other areas, so if its over the height of the cell switch no2 concn
end
no2_iterate(2) = (no2_iterate(2) + no2_layer)*1; % Now units of g no2/cm2
end
no2_iterate = no2_iterate;
end
I suspect that my issue is within the second if-statement where I specify that I want the range to be between two separate variables that I am somehow excluding all variables.
I ended up figuring out the problem. Here is the code that solved my troubles!
Also thank you to commentators for helping me clear some of the noise from my code that didn't do anything practical.
no2_sum_1cm = 0;
gridh_iterate = 0 % starting height in cm
lato = 1;
lono = 1;
no2_iterate_start = 0;
no2_iterate(1:27) = 0;
if gridh_iterate <= gridh(lato,lono,1);
no2_layer = no2_moleccm3(lato,lono,1,12);
for i = 1:gridh(lato,lono,1);
gridh_iterate = gridh_iterate+ 1; % in cm, now compare to gridh(1,1,1) and the other areas, so if its over the height of the cell switch no2 concn
no2_iterate(1) = (no2_iterate(1) + no2_layer)*1; % Now units of g no2/cm2
end
end
gridh_iterate = 0;
if gridh_iterate <= gridh(lato,lono,2) %&& gridh_iterate>gridh(lato,lono,1);
no2_layer = no2_moleccm3(lato,lono,2,12);
for i = 1:gridh(lato,lono,2);
gridh_iterate = gridh_iterate + 1; % in cm, now compare to gridh(1,1,1) and the other areas, so if its over the height of the cell switch no2 concn
no2_iterate(2) = (no2_iterate(2) + no2_layer)*1; % Now units of g no2/cm2
end
end
I ended up realizing since "gridh" variables specified the height of a single cell and not total heights that it was irrelevant to list a range of height data to stay between and that for my purposes I should just set the height of a grid cell I was interesting in as the max, so that my code would iterate through it and then cease.
Related
I am trying to implement the following loop inside of matlab
The difficulty I am having is implementing the sum sign such that I get the correct values. The first row of my X matrix is correct but the second row is not and I cant figure out why.
J = [200 100 300];
k = [3e6 2e6 4e6];
n = 3;
points = 300;
for j = 1:points
w(j)=j;
end
x = zeros(n+1,points);
x(1,:)=1;
for j = 1:points
sumJx = 0;
for i = 2:n+1
sumJx = sum(J(1:i-1)*x(1:i-1,j));
x(i,j) = x(i-1) - (w(j)^2 / k(i-1)) * sumJx;
end
end
f_omega = x(n+1,:);
plot(w,f_omega);
ylim([-40 3])
I am creating a Forward Propagation In the feedforward step, an input pattern is propagated through the network to obtain an output. I have written this in pseudo code and currently attempting to implement this within MATLAB.
There are two errors I currently receive.
Patterns = x'; Desired = y; NHIDDENS = 1; prnout=Desired;
% Patterns become x so number of inputs becomes size of patterns
[NINPUTS,NPATS] = size(Patterns); [NOUTPUTS,NP] = size(Desired);
%apply the backprop here...
LearnRate = 0.15; Momentum = 0; DerivIncr = 0; deltaW1 = 0; deltaW2 = 0;
% Keeps the tan ordering of the examples of x
Inputs1= [Patterns;ones(1,NPATS)]; %Inputs1 = [ones(1,NPATS); Patterns];
% Weight initialisation
Weights1 = 0.5*(rand(NHIDDENS,1+NINPUTS)-0.5);
Weights2 = 0.5*(rand(1,1+NHIDDENS)-0.5);
TSS_Limit = 0.02;
for epoch = 1:10
% FORWARD LOOP
size(NOUTPUTS)
size(NPATS)
for ii = 0: ii < length(NINPUTS)
NOUTPUTS(ii+1) = NPATS(ii);
% Sets bias to 1
NOUTPUTS(1) = 1;
end
for ii = NHIDDENS: ii < NINPUTS
sum = 0;
for ij = 0: ij < ii
sum = sum + deltaW1(ii,ij) * NOUTPUTS(ij);
NOUTPUTS(ii) = tanh(sum);
end
end
Unable to perform assignment because the
left and right sides have a different
number of elements.
Error in mlpts (line 66)
NOUTPUTS(i+1) = NPATS(i);
i am still new to MATLAB and trying to become use to it.
After iterating through the loop
NOUTPUTS = 0 and the error is displayed. I am confused as I am trying to increment NOUTPUTS with ii by 1 through each loop.
I have been able to create the forward propagation with a loop.
for i =3:NNODES
summ = 0;
for j=1:i-1
summ = summ + weights(i,j) * Node_outputs(j);
end
if i == NNODES
Node_outputs(i) = summ
else
Node_outputs(i) = sigmoid(summ);
end
end
Out = Node_outputs(NNODES);
% BOut = ((Node_outputs(NNODES)) * (1 - Node_outputs));
BOut=zeros(1,6);
DeltaWeight = zeros(6,6);
I am attempting to create a gamma distribution in MATLAB; however, I keep receiving the error:
Index in Position 1 exceeds array bounds (must not exceed 100).
Assuming I am reading this correctly, it is referring to variable M that is simply = 2500 (the number of pseudo-random variables I am using for this project).
I was hoping someone can explain what is wrong with my logic and possibly a solution.
alpha = 0.5;
w = gamma_rdn(M,alpha);
x1 = (0.0001:0.001:1); % For plot
figure(5)
subplot(2,1,1);hist(w);title('Histogram of Gamma RDN');
subplot(2,1,2);plot(x1,pdf('gam',x1,alpha,1));title('Theoretical Gamma Density with \alpha = 0.5');
axis([0 1 0 100]);
% The gamma_rdn function is implemented as follows:
function[w] = gamma_rdn(M,alpha)
% Generate random numbers from the gamma distribution with parameter
% alpha <= 1, beta = 1
pe = exp(1);
w = zeros(M,1);
u = rand(100,1);
b = (alpha + pe)/pe;
i = 0;
j = 0;
while j < M
i = i+1;
y = b*u(i,1);
if y <= 1
z = y^(1/alpha);
i = i+1;
if u(i,1) <= exp(-z)
j = j+1;
w(j,1) = z;
else
i = i+1;
end
else
z = -log((b-y)/alpha);
i = i+1;
if u(i,1) <= z^(alpha - 1)
j = j+1;
w(j,1) = z;
else
i = i+1;
end
end
end
if i > 95
u = rand(100,1);
i = 0;
end
end
Is there a particular reason you chose u = rand(100,1)?
The problem is coming because in while loop, as soon as variable i exceeds 100 (say i=101), y = b*u(i,1) becomes invalid. That is, you are trying to access u(101,1) while the size of u is (100,1).
If there's not particular reason, try a large enough size, like, u = rand(10000,1).
I have a 2D matrix of zeros and ones, where the ones indicate a convex figure
I now want to divide this figure (that is the elements of value 1) in nonoverlapping patches of equally the same size, as in this figure
Do you have any suggestion? I could go for mat2cell and have just rectangles, and keep the rectangles with at least one value 1 in them, but I would prefer a more equal division.
For similar problems, I often use a method called 'orthogonal recursive bisection'.
An example of what it does with your circle is in the picture.
As the name suggests, the method divides subdomains into two smaller subdomains,
until the total number of subdomains is the desired value.
My implementation for your case is
function array = ORB(array,nparts)
%
% array = ORB(array,nparts)
%
% Divide the nonzeros of array into nparts equally large,
% approximately square parts.
%
% convert true/false array into 0/1:
ar = array; array = zeros(size(ar)); array(ar) = 1;
% initialize subdivision-admin
istart = 1; iend = nparts; values = 1;
last_value = max(values);
% Divide up the parts that need dividing up
while length(values) < nparts
new_istart = []; new_iend = []; new_values = [];
for i = 1:length(values)
if iend(i) > istart(i)
disp(sprintf('Current values %d should eventually be split into domains %d-%d',values(i),istart(i),iend(i)))
last_value = last_value + 1;
new_istart = [new_istart, istart(i), istart(i) + floor((iend(i)-istart(i)+1)/2)];
new_iend = [new_iend, istart(i) + floor((iend(i)-istart(i)+1)/2)-1, iend(i)];
new_values = [new_values, values(i), last_value];
n = length(new_values);
disp(sprintf('Current values %d should now be split into domains %d and %d, in ratio %d:%d\n', ...
values(i), new_values(n-1:n),new_iend(n-1:n)-new_istart(n-1:n)+1));
array = Split(array,new_values(n-1:n),new_iend(n-1:n)-new_istart(n-1:n)+1);
else
disp(sprintf('Domain %d is done\n',values(i)))
new_istart = [new_istart, istart(i)];
new_iend = [new_iend, iend(i)];
new_values = [new_values, values(i)];
end
end
iend = new_iend; istart = new_istart; values = new_values;
end
for i = 1:nparts
disp(sprintf('Part %d has %d points',i,length(find(array==i))))
end
close all
pcolor(array)
which needs the function Split:
function array = Split(array,parts,sizes)
%
% array = Split(array,parts,sizes)
%
% Change some of the values of array which are now equal to parts(1) into the value parts(2).
% At the end, the ratio
% length(find(array==parts(1))) : length(find(array==parts(2)))
% should be
% sizes(1) : sizes(2)
%
% Calculate sizes of each patch
[i,j] = find(array==parts(1));
npoints = size(i,1); sizes = npoints * sizes/(sizes(1)+sizes(2));
imin = min(i); imax = max(i); jmin = min(j); jmax = max(j);
nmin = 0; nmax = npoints;
if jmax-jmin>imax-imin
% divide domain in (j < jmid) and (jmid <= j)
while jmax > jmin + 1
jmid = (jmax + jmin)/2; n_this = size(find(j<jmid));
if n_this < sizes(1)
jmin = jmid; nmin = n_this;
else
jmax = jmid; nmax = n_this;
end
end
i = i(j>=jmid); j = j(j>=jmid);
else
% divide domain in (i < imid) and (imid <= i)
while imax > imin + 1
imid = (imax + imin)/2; n_this = size(find(i<imid));
if n_this < sizes(1)
imin = imid; nmin = n_this;
else
imax = imid; nmax = n_this;
end
end
j = j(i>=imid); i = i(i>=imid);
end
% Change the values in array
array(sub2ind(size(array),i,j)) = parts(2);
Given the following PDE (non-homogenous heat equation):
ut(x,t) = c2uxx(x,t) + f(x,t)
u(0,t) = u(l,t) = 0
u(x,0) = g(x)
0 < x < l ; t > 0 ; c > 0
I wrote the following code in Matlab, to solve the problem using finite differences:
syms xj tk
% Manually define this values
c = 9;
f(xj,tk) = xj;
g(xj) = 0*xj;
l = 1;
Tmax = 0.1;
% Grid definition
Nx = 50;
Nt = 50;
hx = 1/Nx;
ht = 1/Nt;
x = 0:hx:l;
t = 0:ht:Tmax;
lambda = c^2*ht/hx^2;
% Our target
u = zeros(Nx+1,Nt+1);
% Initial values
for j=1:Nx,
u(j,1) = g(x(j)); % u(x,0) = g(x)
end
for k=1:Nx,
u(1,k+1) = 0; % border condition u(0,t) = 0
for j=2:Nt,
u(j,k+1) = u(j,k) + lambda*(u(j+1,k)-2*u(j,k)+u(j-1,k)) + ht*f(j,k); % the formula here is ok
end
u(Nt,k+1) = 0; % border condition u(l,t) = 0
end
contour3(u)
For some reason that I cant't figure out, data is only appearing in the last columns and in a very strange way.
I'm guessing the implementation of the BC's are doing something nasty. But I don't see it.
Is there something that I'm missing?
Thanks in advance!