help me please. i always get a subscript indices must either be real positive integers or logical error whenever i put 0 value on my "data" how can i get rid of it, i need to have a zero on that one. whenever there is a zero Voltage(1,0) = 1. but I can't get through.
Voltage = [0 1 1 3 4 1; 1 0 5 4 5 3; 6 4 0 4 5 7; 9 3 4 0 6 4; 7 8 5 6 0 7; 4 5 6 7 3 0];
data =[0 2 3 4; 5 6 7 8; 2 3 4 5; 4 5 6 7; 3 4 5 6; 1 3 5 7; 1 2 3 4; 3 4 5 6];
Vm = data(:,1);
Vn = data(:,2);
R = data(:,3);``
X1 = data(:,4);
sz=max(Vn)
y=1:sz
for Vm=data(:,1)
if Vm==0
Voltage(y,Vm)=1
Voltage(y,Vm)=logical(Voltage(y,Vm));
Current = Voltage(y,Vm)-Voltage(y,Vn);
else Vm >= 1
Current = Voltage(y,Vm)-Voltage(y,Vn);
end
end
You are trying to reference a value in the else statement in the Voltage matrix using y but y is not an integer it is an array (or 1d matrix). If you display y you will see that it is 1 2 3 4 5 6. There are several sections of offending code, one of which is:
else Vm >= 1
disp(y) # `y` is not an integer and therefore not a valid index.
Current = Voltage(y,Vm)-Voltage(y,Vn);
To fix it, decide if y should be static or change in the loop.
Let me know if you want a further explanation.
Related
Suppose I have a list of length 2k, say {1,2,...,2k}. The number of possible ways of grouping the 2k numbers into k (unordered) pairs is n(k) = 1*3* ... *(2k-1). So for k=2, we have the following three different ways of forming 2 pairs
(1 2)(3 4)
(1 3)(2 4)
(1 4)(2 3)
How can I use Matlab to create the above list, i.e., create a matrix of n(k)*(2k) such that each row contains a different way of grouping the list of 2k numbers into k pairs.
clear
k = 3;
set = 1: 2*k;
p = perms(set); % get all possible permutations
% sort each two column
[~, col] = size(p);
for i = 1: 2: col
p(:, i:i+1) = sort(p(:,i:i+1), 2);
end
p = unique(p, 'rows'); % remove the same row
% sort each row
[row, col] = size(p);
for i = 1: row
temp = reshape(p(i,:), 2, col/2)';
temp = sortrows(temp, 1);
p(i,:) = reshape(temp', 1, col);
end
pairs = unique(p, 'rows'); % remove the same row
pairs =
1 2 3 4 5 6
1 2 3 5 4 6
1 2 3 6 4 5
1 3 2 4 5 6
1 3 2 5 4 6
1 3 2 6 4 5
1 4 2 3 5 6
1 4 2 5 3 6
1 4 2 6 3 5
1 5 2 3 4 6
1 5 2 4 3 6
1 5 2 6 3 4
1 6 2 3 4 5
1 6 2 4 3 5
1 6 2 5 3 4
As someone think my former answer is not useful, i post this.
I have the following brute force way of enumerating the pairs. Not particularly efficient. It can also cause memory problem when k>9. In that case, I can just enumerate but not create Z and store the result in it.
function Z = pair2(k)
count = [2*k-1:-2:3];
tcount = prod(count);
Z = zeros(tcount,2*k);
x = [ones(1,k-2) 0];
z = zeros(1,2*k);
for i=1:tcount
for j=k-1:-1:1
if x(j)<count(j)
x(j) = x(j)+1;
break
end
x(j) = 1;
end
y = [1:2*k];
for j=1:k-1
z(2*j-1) = y(1);
z(2*j) = y(x(j)+1);
y([1 x(j)+1]) = [];
end
z(2*k-1:2*k) = y;
Z(i,:) = z;
end
k = 3;
set = 1: 2*k;
combos = combntns(set, k);
[len, ~] = size(combos);
pairs = [combos(1:len/2,:) flip(combos(len/2+1:end,:))];
pairs =
1 2 3 4 5 6
1 2 4 3 5 6
1 2 5 3 4 6
1 2 6 3 4 5
1 3 4 2 5 6
1 3 5 2 4 6
1 3 6 2 4 5
1 4 5 2 3 6
1 4 6 2 3 5
1 5 6 2 3 4
You can also use nchoosek instead of combntns. See more at combntns or nchoosek
I have a large dataset as below. From the data, I want to randomly sample based on 'id'. Since the data has 5 ids, I would like to sample 5 ids with replacement and produce a new dataset with observations of sampled ids.
id value var1 var2 …
1 1
1 2
1 3
1 4
2 5
2 6
2 7
3 8
3 9
3 10
4 11
4 12
4 13
5 14
5 15
5 16
Let's suppose, I randomly draw 5 values from 1 to 5 (because there are 5 unique ids) and the result is (2 4 3 2 1). Then, I would like to have this data
id value var1 var2 …
2 5
2 6
2 7
4 11
4 12
4 13
3 8
3 9
3 10
2 5
2 6
2 7
1 1
1 2
1 3
1 4
Here is a sample code for ids varying from 1 through 5.
% data = [1 1; 1 2; 1 3; 1 4; 2 5; 2 6; 2 7; 3 8; 3 9; 3 10; 4 11; 4 12; 4 13;...
% 5 14; 5 15; 5 16];
data = rand(10000000,10);
data(:,1) = randi([1,5], length(data),1);
% Get all the indices from the 1st column;
indxCell = cell(5,1);
for i=1:5
tmpIndx = find(data(:,1) == i);
indxCell{i} = tmpIndx;
end
% Rearrange the indices
randIndx = randperm(5);
randIndxCell = indxCell(randIndx, 1);
% Generate a vector of indices by rearranging the 1st column of data matrix.
numDataPts = length(data);
newIndices = zeros(numDataPts,1);
endIndx = 1;
for i=1:5
startIndx = endIndx;
endIndx = startIndx + length(randIndxCell{i});
newIndices(startIndx:endIndx-1, 1) = randIndxCell{i};
end
newData = data(newIndices,:);
For more unique ids, you could modify the code.
Edits: Modified the data size and also rewrote the 2nd for-loop.
As the title says, I want to find all rows in a Matlab matrix that in certain columns the values in the row are equal with the values in the previous row, or in general, equal in some row in the matrix. For example I have a matrix
1 2 3 4
1 2 8 10
4 5 7 9
2 3 6 4
1 2 4 7
and I want to find the following rows:
1 2 3 4
1 2 3 10
1 2 4 7
How do I do something like that and how do I do it generally for all the possible pairs in columns 1 and 2, and have equal values in previous rows, that exist in the matrix?
Here's a start to see if we're headed in the right direction:
>> M = [1 2 3 4;
1 2 8 10;
4 5 7 9;
2 3 6 4;
1 2 4 7];
>> N = M; %// copy M into a new matrix so we can modify it
>> idx = ismember(N(:,1:2), N(1,1:2), 'rows')
idx =
1
1
0
0
1
>> N(idx, :)
ans =
1 2 3 4
1 2 8 10
1 2 4 7
Then you can remove those rows from the original matrix and repeat.
>> N = N(~idx,:)
N =
4 5 7 9
2 3 6 4
this will give you the results
data1 =[1 2 3 4
1 2 8 10
4 5 7 9
2 3 6 4
1 2 4 7];
data2 = [1 2 3 4
1 2 3 10
1 2 4 7];
[exists,position] = ismember(data1,data2, 'rows')
where the exists vector tells you wheter the row is on the other matrix and position gives you the position...
a less elegant and simpler version would be
array_data1 = reshape (data1',[],1);
array_data2 = reshape (data2',[],1);
matchmatrix = zeros(size(data2,1),size(data1,1));
for irow1 = 1: size(data2,1)
for irow2 = 1: size(data1,1)
matchmatrix(irow1,irow2) = min(data2(irow1,:) == data1(irow2,:))~= 0;
end
end
the matchmatrix is to read as a connectivity matrix where value of 1 indicates which row of data1 matches with which row of data2
I am trying to flip certain parts of a matrix. I can explain better by example. Let's say that I have a matrix
M = [ 1 3 6;
1 2 4;
1 7 1;
2 9 0;
2 8 3;
2 4 2;
2 3 1;
3 6 5;
3 4 5;
3 1 9;
4 2 4;
4 8 6 ]
What I'd like to do here is take any rows with an even number in the first column, and flip the third column elements. The end result would look like this:
1 3 6
1 2 4
1 7 1
2 9 1 *
2 8 2 *
2 4 3 *
2 3 0 *
3 6 5
3 4 5
3 1 9
4 2 6 *
4 8 4 *
Note the rows marked with a star have had the elements of the third column flipped upside-down. The problem I'm having is going through each row like in a for-loop you cannot flip an entire set of rows.
Thanks in advance for any help.
Another time accumarray is the way to go:
A =[ 1 3 6 ;
1 2 4 ;
1 7 1 ;
2 9 0 ;
2 8 3 ;
2 4 2 ;
2 3 1 ;
3 6 5 ;
3 4 5 ;
3 1 9 ;
4 2 4 ;
4 8 6 ]
C = accumarray(A(:,1),A(:,3),[],#(x) {flipud(x)} ); %// get groups according to
%// first column and flip it
C = vertcat(C{:}); %// cell array returned,
%// transform to matrix
mask = ~mod(A(:,1),2); %// mask for even numbers
A(mask,3) = C(mask); %// replace masked values of 3rd column with flipped ones
returns:
A =
1 3 6
1 2 4
1 7 1
2 9 1
2 8 2
2 4 3
2 3 0
3 6 5
3 4 5
3 1 9
4 2 6
4 8 4
Certainly slower, but just for fun in two lines:
C = accumarray(A(:,1),A(:,3),[],#(x) {flipud(x)} );
A(~mod(A(:,1),2),3) = getfield( vertcat(C{:}), {~mod(A(:,1),2)});
%// well no, I won't explain it...
Edit: I assumed your first column just contains integers!
I would suggest you break the problem down into stages, something like so:
Identify blocks you wish to flip
Extract them
Flip them
Replace them
You can identify a set of even numbers using the unique and mod functions, then use a for loop over them and use logical indexing to pull/replace the blocks.
Here, try this
a = magic(5); % Some data in a 5x5 matrix
b = 1:numel(a); % Indices of <a>
Rearrange b however you want, then do a=a(b) to reassign a based on the reassigned indices of b. For example, the following code
disp(a(b));
would just return the elements of a in their original order. For your application this code should work:
a = <your matrix data>
b = 1:numel(a);
b = [b(1:27) fliplr(b(28:31)) b(32:34) fliplr(b(35:36))] % Change this part
a = reshape(a(b),size(a))
You should change b based on whatever you need it to do.
My input is the following:
X = [1 1; 1 2; 1 3; 1 4; 2 5; 1 6; 2 7; 1 8];
X =
1 1
1 2
1 3
1 4
2 5
1 6
2 7
1 8
I am looking to output a new matrix based on the value of the first column. If the value is equal to 1 -- the output will remain the same, when the value is equal to 2 then I would like to output two of the values contained in the second row. Like this:
Y =
1
2
3
4
5
5
6
7
7
8
Where 5 is output two times because the value in the first column is 2 and the same for 7
Here it is (vectorized):
C = cumsum(X(:,1))
A(C) = X(:,2)
D = hankel(A)
D(D==0) = inf
Y = min(D)
Edit:
Had a small bug, now it works.
% untested code:
Y = []; % would be better to pre-allocate
for ii = 1:size(X,1)
Y = [Y; X(ii,2)*ones(X(ii,1),1)];
end