Dynamically change variable name inside a loop in MATLAB - matlab

This script is being used for image processing by multiplying a set of 2000 images with a mask and then summing the values in each frame. These values are entered into a row vector called Intensity.
I am trying to end up with 20 row vectors called intensity1, intesity2...intensity20, is there a straight forward way to change the name of the Intensity row vector upon every loop iteration?
for m=1:20
mask=bigrating(m,m,0);
for n=1:2000
I=sum(sum(imread((sprintf('image%05d.tif',n))).*(mask)));
Intensity(n)=I;
end
save('filepath','Intensity')
end

Because you wanted dynamically named intensity1, intensity2,....intensity20 etc, the following should work for you:
for m = 1:20
mask = bigrating(m,m,0)
for n = 1:2000
I=sum(sum(imread((sprintf('image%05d.tif',n))).*(mask)));
eval(['intensity' num2str(m) ' = I'])
end
save('filepath', ['intensity' num2str(m)])
end

Related

Matlab draw line with plot and dynamic values

I am trying to draw line with plot in matlab app designer. But i dont know how to create line. I am just redrawing point on new coordinates.
This is my code (functions runs each second) (format of plot is plot(PlotUI,X,Y))
function function2(app)
app.timeCounter = app.timeCounter + 1;
plot(app.UIAxes,app.timeCounter,app.newValDblPublic);
end
I will be thankful for any help.
At the moment you are just plotting the current set of values, if you want to plot the historic values too, you need to keep them in an array and plot the entire array.
%When the GUI is first created, start with one value in the array
app.time_values = [0];
app.y_values = [0];
%Inside your function
function function2(app)
app.time_values(end+1) = app.time_values(end)+1; % Add a new value to the array, 1 greater than the last value
app.y_values(end+1) = app.newValDblPublic;
plot(app.UIAxes,app.time_values,app.y_values);
end

How do I adjust this code so that I can enter how many runs I want and it will store each run in a matrix?

I have created this code to generate a 1 set of lottery numbers, but I am trying to make it so that the user can enter how many sets they want (input n), and it will print out as one long matrix of size nX6? I was messing around with a few options from online suggestions, but to no avail. I put the initial for i=1:1:n at the beginning, but I do not know how to store each run into a growing matrix. Right now it still generates just 1 set.
function lottery(n)
for i=1:1:n
xlow=1;
xhigh=69;
m=5;
i=1;
while (i<=m)
lottonum(i)=floor(xlow+rand*(xhigh-xlow+1));
flag=0;
for j=1:i-1
if (lottonum(i)==lottonum(j))
flag=1;
end
end
if flag==0
i=i+1;
end
end
ylow=1;
yhigh=26;
m=1;
lottonum1=floor(ylow+rand*(yhigh-ylow+1));
z = horzcat(lottonum, lottonum1);
end
disp('The lotto numbers picked are')
fprintf('%g ',z)
disp (' ')
The problem is that you are not storing or displaying the newly generated numbers, only the last set. To solve this, initialize z with NaNs or zeros, and later index z to store each set in a row of z, by using z(i,:) = lottonum.
However, you are using i as iterator in the while loop already, so you should use another variable, e.g. k.
You can also set z as an output of the function, so you can use this matrix in some other part of a program.
function z = lottery(n)
% init z
z = NaN(n,6);
for k = 1:n
xlow=1;
xhigh=69;
m=5;
i=1;
while (i<=m)
lottonum(i)=floor(xlow+rand*(xhigh-xlow+1));
flag=0;
for j=1:i-1
if (lottonum(i)==lottonum(j))
flag=1;
end
end
if flag==0
i=i+1;
end
end
ylow=1;
yhigh=26;
lottonum1 = floor(ylow+rand*(yhigh-ylow+1));
z(k,:) = horzcat(lottonum, lottonum1); % put the numbers in a row of z
end
disp('The lotto numbers picked are')
disp(z) % prettier display than fprintf in this case.
disp (' ')
end
The nice answer from rinkert corrected your basic mistakes (like trying to modify your loop iterator i from within the loop => does not work), and answered your question on how to store all your results.
This left you with a working code, however, I'd like to propose to you a different way to look at it.
The porposed architecture is to divide the tasks into separate functions:
One function draw_numbers which can draw N numbers randomly (and does only that)
One function draw_lottery which call the previous function as many times as it needs (your n), collect the results and display them.
draw_lottery
This architecture has the benefit to greatly simplify your main function. It can now be as simple as:
function Draws = draw_lottery(n)
% define your draw parameters
xmin = 1 ; % minimum number drawn
xmax = 69 ; % maximum number drawn
nballs = 5 ; % number of number to draw
% pre allocate results
Draws = zeros( n , nballs) ;
for iDraw=1:1:n
% draw "nballs" numbers
thisDraw = draw_numbers(xmin,xmax,nballs) ;
% add them to the result matrix
Draws(iDraw,:) = thisDraw ;
end
disp('The lotto numbers picked are:')
disp (Draws)
disp (' ')
end
draw_numbers
Instead of using a intricated set of if conditions and several iterators (i/m/k) to branch the program flow, I made the function recursive. It means the function may have to call itself a number of time until a condition is satisfied. In our case the condition is to have a set of nballs unique numbers.
The function:
(1) draws N integer numbers randomly, using randi.
(2) remove duplicate numbers (if any). Using unique.
(3) count how many unique numbers are left Nu
(4a) if Nu = N => exit function
(4b) if Nu < N => Call itself again, sending the existing Nu numbers and asking to draw an additional N-Nu numbers to add to the collection. Then back to step (2).
in code, it looks like that:
function draw = draw_numbers(xmin,xmax,nballs,drawn_set)
% check if we received a partial set
if nargin == 4
% if yes, adjust the number of balls to draw
n2draw = nballs - numel(drawn_set) ;
else
% if not, make a full draw
drawn_set = [] ;
n2draw = nballs ;
end
% draw "nballs" numbers between "xmin" and "xmax"
% and concatenate these new numbers with the partial set
d = [drawn_set , randi([xmin xmax],1,n2draw)] ;
% Remove duplicate
drawn_set = unique(d) ;
% check if we have some more balls to draw
if numel(drawn_set) < nballs
% draw some more balls
draw = draw_numbers(xmin,xmax,nballs,drawn_set) ;
else
% we're good to go, assign output and exit funtion
draw = drawn_set ;
end
end
You can have both functions into the same file if you want.
I encourage you to look at the documentation of a couple of Matlab built-in functions used:
randi
unique

Accessing rows at a fixed interval

I'm looking for a way to update certain elements in a vector [nx113] for every full rotation of my system.
%% # Iterate through timesteps
for tt = 1:nTimeSteps
% # Initialise ink on transfer roller
rollers(2).ink = [zeros(1,98),ones(1,5),zeros(1,113)];
% # Rotate all rollers
for ii = 1:N
rollers(ii).ink(:) = ...
circshift(rollers(ii).ink(:),rollers(ii).rotDirection);
end
% # Update all roller-connections
for ii = 1:N
for jj = 1:nBins(ii)
if(rollers(ii).connections(jj) ~= 0)
index1 = rollers(ii).connections(jj);
index2 = find(ii == rollers(index1).connections);
ink1 = rollers(ii).ink(jj);
ink2 = rollers(index1).ink(index2);
rollers(ii).ink(jj) = (ink1+ink2)/2;
rollers(index1).ink(index2) = (ink1+ink2)/2;
end
end
end
% # Calculate average amount of ink on each roller
for ii = 1:N
averageAmountOfInk(tt,ii) = mean(rollers(ii).ink);
end
rollers(18).TakeOff = averageAmountOfInk*0.6;
end
the vector rollers(2).ink is the vector i'd like to update. currently the vector is populated only once so i have ones from row 98:103. I would like this range of elements to be populated for each 'rotation' of my system not just the first time.
The reason - I'm trying to show ink being added intermittently from only a small section of the roller surface, hence the need for only five cells to be populated.
i thought that if i iterated from 1 to the number of timesteps, in steps size nBins-Max in the loop:
for tt = 1:nBins_max:nTimeSteps
this doesn't seem to be what i'm after.
I'm also hoping to remove ink from the system at the end. for every revolution i would like to be able to remove a percentage of ink on each rotation so it does not stay in the system (as if it was being printed onto a sheet and taken away).
Hopefully someone can understand this and perhaps offer some advice on how to proceed on either or both of my issues.
Your explanation doesn't quite match your code (or vice-versa if you prefer) so I'm not entirely sure what you want to do, but the following may help you towards a solution or towards expressing your problem more clearly.
The vector rollers(2).ink has 1 row and 216 columns, so an operation such as rollers(2).ink(98:103) = something is not updating rows 98 through to 103. Note also that element 98 of that vector is initialised to 0, it's not included in the elements which are initialised to 1.
You write that you want to update a range of the elements in that vector, then write a loop statement for tt = 1:nBins_max:nTimeSteps which strides over a vector of time steps. Surely you want to write something like rollers(2).ink(99:103) = new_values.
As for removing ink from the rollers at every rotation, you could just execute a line such as rollers(2).ink = rollers(2).ink * 0.975 every rotation; obviously you'll want to replace the removal rate of 2.5% every rotation that I have chosen with whatever is right for your simulation.

Output loop result in Matlab

Hi have this code and I don't know how to put the output result with every pixel.I think the output code are not well defined.
EDIT:
I'm going to try to explain the code:
% I have an image
imagen1=imread('recor.tif');
imagen2= double(imagen1);
band1= imagen2(:,:,1);
% I preallocate the result (the image size is 64*89*6)
yvan2= zeros(61,89,1);
% For every pixel of the image, I want to get one result (each one is different).
for i = 1 : nfiles
for j = 1 : nrows
for i = 1:numel(band1)
% I'm doing this because I've to multiply the results of this interpolation with that result a2ldb1y= ldcm_1(:,1). This vector has a length of 2151x1 and I need to muliply the result of the interpolation for (101:267) position on the vector, this is the reason because I'm doing the interpolation since 101 to 267 (also because I don't have that values).
interplan= interp1(van1,man2,t2,'spline');
ma(96) = banda1a(i); % I said 96, because I want to do an interpollation
end
van1= [101 96 266]';
mos1= ma(134);
van2= [0 pos1 0];
t= 101:267;
t2= t';
xi= 101:1:267;
xi2=xi';
interplan= interp1(van1,van2,t2,'spline');
% After this, I 'prepare' the vector.
out=zeros(2151,1)
out(101:267) = interplan;
% And then, I do all this operation (are important for the result)
a2ldb1y= ldcm_1(:,1);
a2ldsum_pesos1= sum(a2ldb1y);
a2l7dout1_a= a2ldb1y.*out;
a2l7dout1_b= a2l7dout1_a./a2ldsum_pesos1;
a2l7dout1_c= sum(a2l7dout1_b);
% And the result a2l7dout1_c I want it for every pixel (the results are different because every pixel has a different value...)
**yvan2(:,:,1)= [a2l7dout1_c];**
end
end
Thanks in advance,
I'm shooting in the dark here, but I think you're looking for:
yvan2(i, j, 1)= a2l7dout1_c;
instead of:
yvan2(:,:,1)= [a2l7dout1_c];
and thus your output should be stored in the variable yvan2 after the loops are done.
P.S
Some issues in your code:
Why do you have two loops using the same iteration variable i? Your calculations are probably incorrect since i is being modified by two for loops.
Why do you even need the second loop? Each iteration overruns the value of ma(134) set by the previous iteration. You can just replace the entire loop with:
ma(134) = banda1a(numel(band1))
You shouldn't be using the names i and j for loop variables. They are already reserved for the imaginary unit (that is, sqrt(-1)), so MATLAB needs extra processing time for name resolution. You'd rather use other loop variable names instead, even ii and jj.

Mark values from loop for each iteration

I want to mark each value that comes out of my loop with a value.
Say I have a variable number of values that come out of each iteration. I want those values to be labeled by which iteration they came out of.
like
1-1,
2-1,
3-1,
1-2,
2-2,
3-2,
4-2,
etc.
where the first number is the value from the loop and the second is counting which iteration it came from.
I feel like there is a way I just cant find it.
ok so here is some code.
for c=1:1:npoints;
for i=1:1:NN;
if ((c-1)*spacepoints)<=PL(i+1) && ((c-1)*spacepoints)>=PL(i);
local(c)=((c)*spacepoints)-PL(i);
end
if ((c-1)*spacepoints)>=PL(NN);
local(c)=((c)*spacepoints)-PL(NN);
element(i)=NN;
end
end
I want to mark each local value with the iteration it came from for the i:NN. PL is a vector and the output is a set of vectors for each iteration.
For this sort of quick problem I like to create a cell array:
for k = 1:12
results{k} = complicated_function(...);
end
If the output is really complicated, then I return a struct with fields relating to the outputs:
for k = 1:12
results{k}.file = get_filename(...);
results{k}.result = ...;
end
Currently as it is right now, in your inner 1:NN loop, your local(c) variable is being updated or overwritten. You never apply the previous value of local, so it is not some iterative optimization algorithm(?)...
Perhaps an easy solution is to change the size/type of local from a vector to a matrix. Let's say that local is of size [npoints 1]. Instead you make it of size [npoints NN]. It is now a 2d-array (a matrix of npoints rows and NN columns). use the second dimension to store each (assumed column) vector from the inner loop:
local = zeros([npoints NN]);
%# ... code in bewteen ...
for c=1:1:npoints;
for i=1:1:NN;
if ((c-1)*spacepoints)<=PL(i+1) && ((c-1)*spacepoints)>=PL(i);
local(c, i)=((c)*spacepoints)-PL(i);
end
if ((c-1)*spacepoints)>=PL(NN);
local(c, i)=((c)*spacepoints)-PL(NN);
element(i)=NN;
end
end
end
The c'th row of your local matrix will then corresponds to the NN values from the inner loop. Please note that I have assumed your vector to be a column vector - if not, just change the order of the sizes.