N = 500;
pattern = zeros(N,N);
grid on
plot(pattern)
% gets coordinates of modified cells
[x,y] = ginput;
% convert coordinates to integers
X = uint8(x);
Y = uint8(y);
% convert (X,Y) into linear indices
indx = sub2ind([N,N],x,y);
% switch desired cells on (value of 1)
pattern(indx) = 1;
I'm trying to assign several elements of a zeros array the value of 1. Basically I want to create an interactive plot where the user decides what cells he wants to turn on and then save his drawing as a matrix. In Python it's very simple to use the on_click with Matplotlib, but Matlab is weird and I can't find a clear answer. What's annoying is you can't see where you clicked until you save your changes and check the final matrix. You also can't erase a point if you made a mistake.
Moreover I get the following error : Error using sub2ind Out of range subscript. Error in createPattern (line 12) indx = sub2ind([N,N],X,Y);
Any idea how to fix it?
function CreatePattern
hFigure = figure;
hAxes = axes;
axis equal;
axis off;
hold on;
N = 3; % for line width
M = 20; % board size
squareEdgeSize = 5;
% create the board of patch objects
hPatchObjects = zeros(M,M);
for j = M:-1:1
for k = 1:M
hPatchObjects(M - j+ 1, k) = rectangle('Position', [k*squareEdgeSize,j*squareEdgeSize,squareEdgeSize,squareEdgeSize], 'FaceColor', [0 0 0],...
'EdgeColor', 'w', 'LineWidth', N, 'HitTest', 'on', 'ButtonDownFcn', {#OnPatchPressedCallback, M - j+ 1, k});
end
end
Board = zeros(M,M);
playerColours = [1 1 1; 0 0 0];
xlim([squareEdgeSize M*squareEdgeSize]);
ylim([squareEdgeSize M*squareEdgeSize]);
function OnPatchPressedCallback(hObject, eventdata, rowIndex, colIndex)
% change FaceColor to player colour
value = Board(rowIndex,colIndex);
if value == 1
set(hObject, 'FaceColor', playerColours(2, :));
Board(rowIndex,colIndex) = 0; % update board
else
set(hObject, 'FaceColor', playerColours(1, :));
Board(rowIndex,colIndex) = 1; % update board
end
end
end
I found this link and modified the code to be able to expand the board and also select cells that have been turned on already to switch them off.
Now I need a way to extract that board value to save the array.
Related
Suppose I have an array of length 15
x = randi([0 5], 1,15);
I want to sum every 3 elements of x together and put each sum in a new array called y, as in the following:
y = [y1 y2 y3 y4 y5];
Please help me in doing that in Matlab using for loops.
Here's a vectorized approach that automatically deals with a possible smaller last chunk:
x = randi([0 5], 1, 15); % example data
N = 3; % chunk size
y = accumarray(ceil((1:numel(x))/N).', x(:));
you can use reshape as follows:
y = sum(reshape(x,3,[]))
This reshapes your vector x to an array 3 by whatever is left, then sum along right dimension...
For the case the # of elements you want to sum doesnt add up to the total length of the vector, you can pad with zeros or NaN at the end to make it work. Here's I chose adding zeros:
x = randi([0 5], 1,15);
n = 4 ; % sum every n elements (which is the number of rows in the reshape)
try
y = sum(reshape(x, n, []));
catch
disp('added trailing zeros!')
x(numel(x) + (n - mod(numel(x), n))) = 0;
y = sum(reshape(x, n, []));
end
(you can do this with an if condition instead, I just like try catch more here)
Using for loops:
y = zeros(1,5);
for i = 1:5
idx = (i-1)*3 + 1:(i-1)*3 + 3;
y(i) = sum(x(idx));
end
Using a reference variable Target that is used to indicate the start position of each partition the loop below can be achieved. If you would only like to use only loops an alternative inner loop can be done. This method works almost on the same premise as windowing.
Method 1: Single For-Loop with Indexing
x = randi([0 5], 1,15);
y = zeros(1,length(x)/3);
Index = 1;
for Target = 1: +3: 15
Partition = x(Target:Target+2);
y(1,Index) = sum(Partition);
Index = Index + 1;
end
Method 2: Outer and Inner For-Loops
x = randi([0 5], 1,15);
y = zeros(1,length(x)/3);
Partition = zeros(1,3);
Index = 1;
for Target = 1: +3: 15
for Column = 1: +1: 3
Partition(1,Column) = x(1,Target+Column-1);
end
y(1,Index) = sum(Partition);
Index = Index + 1;
end
I have a matrix A of dimension m-by-n composed of zeros and ones, and a matrix J of dimension m-by-1 reporting some integers from [1,...,n].
I want to construct a matrix B of dimension m-by-n such that for i = 1,...,m
B(i,j) = A(i,j) for j=1,...,n-1
B(i,n) = abs(A(i,n)-1)
If sum(B(i,:)) is odd then B(i,J(i)) = abs(B(i,J(i))-1)
This code does what I want:
m = 4;
n = 5;
A = [1 1 1 1 1; ...
0 0 1 0 0; ...
1 0 1 0 1; ...
0 1 0 0 1];
J = [1;2;1;4];
B = zeros(m,n);
for i = 1:m
B(i,n) = abs(A(i,n)-1);
for j = 1:n-1
B(i,j) = A(i,j);
end
if mod(sum(B(i,:)),2)~=0
B(i,J(i)) = abs(B(i,J(i))-1);
end
end
Can you suggest more efficient algorithms, that do not use the nested loop?
No for loops are required for your question. It just needs an effective use of the colon operator and logical-indexing as follows:
% First initialize B to all zeros
B = zeros(size(A));
% Assign all but last columns of A to B
B(:, 1:end-1) = A(:, 1:end-1);
% Assign the last column of B based on the last column of A
B(:, end) = abs(A(:, end) - 1);
% Set all cells to required value
% Original code which does not work: B(oddRow, J(oddRow)) = abs(B(oddRow, J(oddRow)) - 1);
% Correct code:
% Find all rows in B with an odd sum
oddRow = find(mod(sum(B, 2), 2) ~= 0);
for ii = 1:numel(oddRow)
B(oddRow(ii), J(oddRow(ii))) = abs(B(oddRow(ii), J(oddRow(ii))) - 1);
end
I guess for the last part it is best to use a for loop.
Edit: See the neat trick by EBH to do the last part without a for loop
Just to add to #ammportal good answer, also the last part can be done without a loop with the use of linear indices. For that, sub2ind is useful. So adopting the last part of the previous answer, this can be done:
% Find all rows in B with an odd sum
oddRow = find(mod(sum(B, 2), 2) ~= 0);
% convert the locations to linear indices
ind = sub2ind(size(B),oddRow,J(oddRow));
B(ind) = abs(B(ind)- 1);
I'm still confused why am not able to know the results of this small algorithm of my array. the array has almost 1000 number 1-D. am trying to find the peak and the index of each peak. I did found the peaks, but I can't find the index of them. Could you please help me out. I want to plot all my values regardless the indexes.
%clear all
%close all
%clc
%// not generally appreciated
%-----------------------------------
%message1.txt.
%-----------------------------------
% t=linspace(0,tmax,length(x)); %get all numbers
% t1_n=0:0.05:tmax;
x=load('ww.txt');
tmax= length(x) ;
tt= 0:tmax -1;
x4 = x(1:5:end);
t1_n = 1:5:tt;
x1_n_ref=0;
k=0;
for i=1:length(x4)
if x4(i)>170
if x1_n_ref-x4(i)<0
x1_n_ref=x4(i);
alpha=1;
elseif alpha==1 && x1_n_ref-x4(i)>0
k=k+1;
peak(k)=x1_n_ref; // This is my peak value. but I also want to know the index of it. which will represent the time.
%peak_time(k) = t1_n(i); // this is my issue.
alpha=2;
end
else
x1_n_ref=0;
end
end
%----------------------
figure(1)
% plot(t,x,'k','linewidth',2)
hold on
% subplot(2,1,1)
grid
plot( x4,'b'); % ,tt,x,'k'
legend('down-sampling by 5');
Here is you error:
tmax= length(x) ;
tt= 0:tmax -1;
x4 = x(1:5:end);
t1_n = 1:5:tt; % <---
tt is an array containing numbers 0 through tmax-1. Defining t1_n as t1_n = 1:5:tt will not create an array, but an empty matrix. Why? Expression t1_n = 1:5:tt will use only the first value of array tt, hence reduce to t1_n = 1:5:tt = 1:5:0 = <empty matrix>. Naturally, when you later on try to access t1_n as if it were an array (peak_time(k) = t1_n(i)), you'll get an error.
You probably want to exchange t1_n = 1:5:tt with
t1_n = 1:5:tmax;
You need to index the tt array correctly.
you can use
t1_n = tt(1:5:end); % note that this will give a zero based index, rather than a 1 based index, due to t1_n starting at 0. you can use t1_n = 1:tmax if you want 1 based (matlab style)
you can also cut down the code a little, there are some variables that dont seem to be used, or may not be necessary -- including the t1_n variable:
x=load('ww.txt');
tmax= length(x);
x4 = x(1:5:end);
xmin = 170
% now change the code
maxnopeaks = round(tmax/2);
peaks(maxnopeaks)=0; % preallocate the peaks for speed
index(maxnopeaks)=0; % preallocate index for speed
i = 0;
for n = 2 : tmax-1
if x(n) > xmin
if x(n) >= x(n-1) & x(n) >= x(n+1)
i = i+1;
peaks(i) = t(n);
index(i) = n;
end
end
end
% now trim the excess values (if any)
peaks = peaks(1:i);
index = index(1:i);
I want to generate an arbitrary linear signal from matlab function block in simulink. I have to use this block because then, I want to control when i generate the signal by a sequence in Stateflow. I try to put the out of function as a structure with a value field and another time as the following code:
`function y = sig (u)
if u == 1
t = ([0 10 20 30 40 50 60]);
T = [(20 20 40 40 60 60 0]);
S.time = [t '];
S.signals (1) values = [T '].;
S.signals (1) = 1 dimensions.;
else
N = ([0 0 0 0 0 0 0]);
S.signals (1) values = [N '].;
end
y = S.signals (1). values
end `
the idea is that u == 1 generates the signal, u == 0 generates a zero output.
I also try to put the output as an array of two columns (one time and another function value) with the following code:
function y = sig (u)
if u == 1
S = ([0, 0]);
cant = input ('Number of points');
for n = Drange (1: cant)
S (n, 1) = input ('time');
S (n, 2) = input ('temperature');
end
y = [S]
else
y = [0]
end
end
In both cases I can not generate the signal.
In the first case I get errors like:
This structure does not have a field 'signals'; new fields can not be added When structure has-been read or used
or
Error in port widths or dimensions. Output port 1 of 'tempstrcutsf2/MATLAB Function / u' is a one dimensional vector with 1 elements.
or
Undefined function or variable 'y'. The first assignment to a local variable Determines its class.
And in the second case:
Try and catch are not supported for code generation,
Errors occurred During parsing of MATLAB function 'MATLAB Function' (# 23)
Error in port widths or dimensions. Output port 1 of 'tempstrcutsf2/MATLAB Function / u' is a one dimensional vector with 1 elements.
I'll be very grateful for any contribution.
PD: sorry for my English xD
You have many mistakes in your code
you have to read more about arrays and structs in matlab
here S = ([0, 0]); you're declare an array with only two elements so the size will be static
There is no function called Drange in mtlab except if it's yours
See this example with strcuts and how they are created for you function
function y = sig(u)
if u == 1
%%getting fields size
cant = input ('Number of points\r\n');
%%create a structure of two fields
S = struct('time',zeros(1,cant),'temperature',zeros(1,cant));
for n =1:cant
S.time(n) = input (strcat([strcat(['time' num2str(n)]) '= ']));
S.temperature(n) = input (strcat([strcat(['temperature'...
num2str(n)]) '= ']));
end
%%assign output as cell of struct
y = {S} ;
else
y = 0 ;
end
end
to get result form y just use
s = y{1};
s.time;
s.temperature;
to convert result into 2d array
2dArray = [y{1}.time;y{1}.temperature];
Work with arrays
function y = sig(u)
if u == 1
cant = input ('Number of points\r\n');
S = [];
for n =1:cant
S(1,n) = input (strcat([strcat(['time' num2str(n)]) '= ']));
S(2,n) = input (strcat([strcat(['temperature'...
num2str(n)]) '= ']));
end
y = S;
else
y = 0 ;
end
end
I have a column vector (V1) of real numbers like:
123.2100
125.1290
...
954.2190
If I add, let's say, a number 1 to each row in this vector, I will get (V2):
124.2100
126.1290
...
955.2190
I need to find out how many elements from V2 are inside some error-window created from V1. For example the error-window = 0.1 (but in my case every element in V1 has it's own error window):
123.1100 123.3100
125.0290 125.2290
...
954.1190 954.3190
I can create some code like this:
% x - my vector
% ppm - a variable responsible for error-window
window = [(1-(ppm/1000000))*x, (1+(ppm/1000000))*x]; % - error-window
mdiff = 1:0.001:20; % the numbers I will iteratively add to x
% (like the number 1 in the example)
cdiff = zeros(length(mdiff),1); % a vector that will contain counts of elements
% corresponding to different mdiff temp = 0;
for i = 1:length(mdiff)
for j = 1:size(window,1)
xx = x + mdiff(i);
indxx = find( xx => window(j,1) & xx <= window(j,2) );
if any(indxx)
temp = temp + length(indxx); %edited
end
end
cdiff(i) = temp;
temp = 0;
end
So, at the end cdiff will contain all the counts corresponding to mdiff. The only thing, I would like to make the code faster. Or is there a way to avoid using the second loop (with j)? I mean to directly use a multidimensional condition.
EDIT
I decided to simpify the code like this (thanking to the feedback I got here):
% x - my vector
% ppm - a variable responsible for error-window
window = [(1-(ppm/1000000))*x, (1+(ppm/1000000))*x]; % - error-window
mdiff = 1:0.001:20; % the numbers I will iteratively add to x
% (like the number 1 in the example)
cdiff = zeros(length(mdiff),1); % a vector that will contain counts of elements
% corresponding to different mdiff temp = 0;
for i = 1:length(mdiff)
xx = x + mdiff(i);
cdiff(i) = sum(sum(bsxfun(#and,bsxfun(#ge,xx,window(:,1)'),bsxfun(#le,xx,window(:,2)'))));
end
In this case the code works faster and seems properly
add = 1; %// how much to add
error = .1; %// maximum allowed error
V2 = V1 + add; %// build V2
ind = sum(abs(bsxfun(#minus, V1(:).', V2(:)))<error)>1; %'// index of elements
%// of V1 satisfying the maximum error condition. ">1" is used to because each
%// element is at least equal to itself
count = nnz(ind);
Think this might work for you -
%%// Input data
V1 = 52+rand(4,1)
V2 = V1+1;
t= 0.1;
low_bd = any(abs(bsxfun(#minus,V2,[V1-t]'))<t,2); %%//'
up_bd = any(abs(bsxfun(#minus,V2,[V1+t]'))<t,2); %%//'
count = nnz( low_bd | up_bd )
One could also write it as -
diff_map = abs(bsxfun(#minus,[V1-t V1+t],permute(V2,[3 2 1])));
count = nnz(any(any(diff_map<t,2),1))
Edit 1:
low_bd = any(abs(bsxfun(#minus,V2,window(:,1)'))<t,2); %%//'
up_bd = any(abs(bsxfun(#minus,V2,window(:,2)'))<t,2); %%//'
count = nnz( low_bd | up_bd )
Edit 2: Vectorized form for the edited code
t1 = bsxfun(#plus,x,mdiff);
d1 = bsxfun(#ge,t1,permute(window(:,1),[3 2 1]));
d2 = bsxfun(#le,t1,permute(window(:,2),[3 2 1]));
t2 = d1.*d2;
cdiff_vect = max(sum(t2,3),[],1)';