I'm trying to save values from a while loop into vectors. I have the following code.
Delta_P = 1;
count = 0;
while Delta_P > 0.00001
x1 = ((y1*p)/(c1*p1));
x2 = ((y2*p)/(c2*p2));
c1 = exp(A*x2.^2);
c2 = exp(A*x1.^2);
p_update = 1/(y1/(c1*p1)+(y2/(c2*p2)));
Delta_P = abs(p-p_update);
p = p_update;
count = count + 1;
end
I need to save p, x1, and x2 into vectors. The loop must also stay in a while loop. I have no idea on how I would go about saving them into vectors.
Thanks.
In your loop change only:
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x1(count) = ((y1*p)/(c1*p1));
x2(count) = ((y2*p)/(c2*p2));
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p(count) = p_update;
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In addition to #Dans answer - you would need to either:
Change the initialisation of count to be count = 1;
or
Move the increment of count to be before you use it for x1(count) ....
Related
I build some program in Matlab for "Histograma matching".
When I'm trying to implement the function "conVector" I get the error
"Index exceeds array bounds." anyone can help me with this error?
Here is my full code. Thank you!
function [newImage] = histShape (srcimg,destimg)
%find the histogram of the image
src = imgHist(srcimg);
dest = imgHist(destimg);
sna = normalizationHist(src);
dna = normalizationHist(dest);
conVector(sna,dna);
end
function [Hist] = imgHist (img)
[Rows,Cols] = size(img);
Hist = zeros(1,256);
for i=1:Rows
for j=1:Cols
Hist(img(i,j)+1)=Hist(img(i,j)+1)+1;
end
end
end
function [Ahist] = normalizationHist (hist)
[Rows,Cols] = size(hist);
Ahist = hist;
for i=2:256
Ahist(i)=Ahist(i-1)+hist(i);
end
Ahist = Ahist/(Rows*Cols);
end
function [cv] = conVector(SNA,DNA)
cv=zeros(1,257);
s = 1;
d = 1;
while s<=256
if DNA(d)<SNA(s)
d = d+1;
else
cv(s)=d;
s = s+1;
end
end
end
If all values in DNA(d:end) are smaller then the value in SNA(s) than the loop keep adding 1 to d but not to s, and finally goes out of bound because it conditioned only by s.
I guess you should either take the s = s+1 out of the inner condition, so it will be executed on every iteration, or add a condition on d to the loop, or convert it to a for loop.
The code segment I'm working on is given below:
NphaseSteps = 6;
phases = exp( 2*pi*1i * (0:(NphaseSteps-1))/NphaseSteps );
i = 1;
while i <= 10 %number of iterations
ind = randi([1 NphaseSteps],10,10);
inField{i} = phases(ind);
save('inField.mat', 'inField')
i = i + 1;
end
Now, what I want is to keep track of these randomly created matrices "inField{i}" and eliminate the ones that are equal to each other. I know that I can use "if" condition but since I'm new to programming I don't know how to use it more efficiently so that it doesn't take too much time. So, I need your help for a fast working program that does the job. Thanks in advance.
My actual code segment (after making the changes suggested by #bisherbas) is the following. Note that I actually want to use the variable "inField" inside the loop for every random created matrix and the loop advances only if the result satisfies a specific condition. So, I think the answer given by #bisherbas doesn't really eliminate the equal inField matrices before they are used in the calculation. This is, of course, my fault since I didn't declare that in the beginning.
NphaseSteps = 6;
phases = exp( 2*pi*1i * (0:(NphaseSteps-1))/NphaseSteps );
nIterations = 5;
inField = cell(1,nIterations);
i = 1;
j = 1;
while i <= nIterations % number of iterations
ind = randi([1 NphaseSteps],TMsize,TMsize);
tmp = phases(ind);
idx = cellfun(#(x) isequal(x,tmp),inField);
if ~any(idx)
inField{i} = tmp;
end
j = j+1;
outField{i} = TM * inField{i};
outI = abs(outField{i}).^2;
targetIafter{i} = abs(outField{i}(focusX,focusY)).^2;
middleI = targetIafter{i} / 2;
if (max(max(outI)) == targetIafter{i})...
&& ( sum(sum((outI > middleI).*(outI < max(max(outI))))) == 0 )
save('inFieldA.mat', 'inField')
i = i + 1;
end
if mod(j-1,10^6) == 0
fprintf('The number of random matrices tried is: %d million \n',(j-1)/10^6)
end
end
Additionally, I've written a seemingly long expression for my loop condition:
if (max(max(outI)) == targetIafter{i})...
&& ( sum(sum((outI > middleI).*(outI < max(max(outI))))) == 0 )
save('inFieldA.mat', 'inField')
i = i + 1;
end
Here I want a maximum element at some point (focusX, focusY) in the outField matrix. So the first condition decides whether the focus point has the maximum element for the matrix. But I additionally want all other elements to be smaller than a specific number (middleI) and that's why the second part of the if condition is written. However, I'm not very comfortable with this second condition and I'm open to any helps.
Try this:
NphaseSteps = 6;
phases = exp( 2*pi*1i * (0:(NphaseSteps-1))/NphaseSteps );
i = 1;
inField = cell(1,NphaseSteps);
while i <= NphaseSteps %number of iterations
ind = randi([1 NphaseSteps],NphaseSteps,NphaseSteps);
tmp = phases(ind);
idx = cellfun(#(x) isequal(x,tmp),inField);
if ~any(idx)
inField{i} = tmp;
end
save('inField.mat', 'inField')
i = i + 1;
end
Read more on cellfun here:
https://www.mathworks.com/help/matlab/ref/cellfun.html
I have a for loop that is storing values. For some reason, it is calculating values for all the number up to and including those in the for loop, instead of just the ones in the array.
t = 3600:50:172800;x = 0.1;y = 0; ro = 0.1;
T = zeros(1,length(t));
for Cm = 1E6:1E6:4E6
for i = 1:length(t)
T = T_ILS(x,y,ro,Cm,t);
Tall(Cm,:) = [T];
end
end
The error I get is "Requested 2000000x3385 array exceeds maximum array size preferences". I would like the for loop to calculate just the Cm values and not every number in between.
You are not computing every value in between, but your indices are messed up. Cm takes values in the millions, but you use it to index Tall(Cm,:). You probably want
t = 3600:50:172800;x = 0.1;y = 0; ro = 0.1;
T = zeros(1,length(t));
Cm = 1E6:1E6:4E6;
for j = 1:length(Cm)
for i = 1:length(t)
T(i) = T_ILS(x,y,ro,Cm(j),t(i));
end
Tall(j,:) = [T];
end
Notice that the main function call assigns to T(i) and uses t(i) in the function arguments to justify the existence of the for loop.
In the inner loop, T is the output of the function T_ILS, using the same arguments each time.
for i = 1:length(t)
T = T_ILS(x,y,ro,Cm,t);
Tall(Cm,:) = [T];
end
I don't know what this function computes, but you probably wanted to do this instead
for i = 1:length(t)
T = T_ILS(x,y,ro,Cm,t(i));
Tall(Cm,:) = [T];
end
to account for each value of the vector t, or even better:
for t = 3600:50:172800
T = T_ILS(x,y,ro,Cm,t);
Tall(Cm,:) = [T];
end
EDIT: Also, to make this answer complete, I'd like to merge #MadPhysicist's answer with mine. The result would be
Cm = 1E6:1E6:4E6; x = 0.1;y = 0; ro = 0.1;
T = zeros(1,length(t));
for i = 1:length(Cm)
for t = 3600:50:172800;
T = T_ILS(x,y,ro,Cm(i),t);
Tall(i,:) = [T];
end
end
I need to save results of a for loop in a matrix where its size is 4*1?
My function:
function test()
for j=2:2:8
h= 3*j
end
end
results:
h=6
h=12
h=18
h=24
Thank you in advance.
You can do this via loop, and than you should first create the matrix:
function test()
n = 2:2:8;
h = zeros(length(n),1)
counter = 1;
for j = n
h(counter) = 3*j
counter = counter+1;
end
end
But that is the long and non-efficient way, instead you should use vectorization:
n = 2:2:8;
h = n.'*3
or just: h = (2:2:8).'.*3;
that's it.
I'm facing an issue with this simple Fibonacci number generator program:
function f = fibonr(n)
f(1) = 1;
f(2) = 1;
for i = 3:n
f(i) = f(i-1) + f(i-2);
end
end
If I want to display only the n-th number of the sequence, what adjustments should I make?
function f = fibonr(n)
f = zeros(n,1); %//initialise the output array
f(1,1) = 1;
f(2,1) = 1;
for ii = 3:n
f(ii,1) = f(ii-1,1) + f(ii-2,1);
end
%//create a string with text and variables
str = sprintf('The %d th number in the Fibonacci sequence is %d',n,f(ii,1));
disp(str) %//display your output.
end
first up: don't use i as a variable. Secondly, I switched to using column vectors, since MATLAB processes them faster, as well as I initialised the array, which is way faster (hence the shiny orange wiggles below your f(i)= line).
Call your function:
output = fibonr(10);
The 10 th number in the Fibonacci sequence is 55
If you use e.g. n=20 and still want the 10th argument just call output(10)
if you want the specified output right away you can use nargin. This code will give you all of the sequence if you call fibonr(n), or you can specify a vector to get the fibonacy numbers at said positions. If you are interested in both, your specified output and all the numbers, you can call the function with:
[output, fibnumbers] = fibonr(n,v);
function [output,f] = fibonr(n,v)
f(1) = 1;
f(2) = 1;
for i = 3:n
f(i) = f(i-1) + f(i-2);
end
if nargin() > 1
output = f(v);
else
output = f;
end