I know how to write the program with a given number of entries, but not when if the number of entries are n:. Basically I think I need a loop but I can't get it to work properly.
This is a code that works fine when having 3 entries. % is what I put in. I want to create a vector with specific position and values, this is a example how the vector would look like:
X = [1;0;0;0;0;0;0;0;0;0;0;0;0;0;99;0;0;0;0;99]
and the code for it:
n1 = input('Determine value for case:'); %n1 = 1
n2 = input('Determine value for case:'); %n2 = 15
n3 = input('Determine value for case:'); %n3 = 20
X = zeros(20,1);
X(n1) = input('Determine position '); %1
X(n2) = input('Determine position '); %99
X(n3) = input('Determine position '); %99
But for n entries, I need a loop I figured. (the vector may still be 20x1)
for n = 1:entries (%entries are 3, so 3 loops)
n = n+1
n = input('Determine value for case :');
X =zeros(20,1);
X(n) = input('Determine position:')
end
But I can't just get it to work
thanks in advance
Not sure exactly what you are trying to achieve, but I think that you can fix your loop as follows:
entries = 3;
X =zeros(20,1);
for ni = 1:entries
n = input('Determine value for case :');
X(n) = input('Determine position:');
end
Related
I need some help to store values in MATLAB using the following code:
for n = 1:some number
iter = 0;
while % condition
iter = iter + 1 ;
for k = 1:9
% call the integrator 9 times
[t,s] = ode113(#(t,y) eqns, [0 t{k}], X{k}, options);
% X{k} contains 9 initial conditions where each has 6 values
x{k} = s(:,1:6)
% x{k} = stores each arc from integration
x = 1x9 cell array where each cell is #rowsx6
end
end
state(n,:) = x;
end
The issue I am having is that state does not have all n values of x. For example, if n = 2, state is size 2x9 BUT only the x values for n = 2 is stored; nothing is saved for n = 1. I also tried: state{n}(iter,:) inside the while loop and it also only stores the x data from the last iteration. It appears that the variable state is being overwritten. Can someone please point me in the right direction?
got it! thanks for inputs. variable was not assigned properly.
I have a vector named signal consisting of 300001 values. In each iteration of the for loop, I want to pick up 2000 consecutive values from this vector and store it in another vector X (X is 1*2000 vector)
The code is as follows:
D = 1:300001;
A = zeros(1,2000);
r=1;
n=0;
m=1;
for i=1:300001
for p = (1+(2000*n)):(r*2000)
while m<2000
A(1,m)= signal(1,p);
%disp (m);
m = m+1;
end
end
r = r+1;
n = n+1;
m = 1;
end
But it gives me the error "Index exceeds matrix dimensions.
Can somebody help me out with a better way to do it?
this would work
signal = ones(1,30000);
index1= 1:2000:length(signal);
index2= 2000:2000:length(signal);
for i=1:length(index1)
A = signal(index1(i):index2(i));
end
or this
signal = ones(1,30000);
temp = reshape(signal,2000,[]);
for i = 1:size(temp,2)
A=temp(:,i);
end
I have x and y data that has n number of points in each of the arrays.
I want to use polyfit on portions of the data.
I want to divide the data into a certain number of divisions(numDivisions).
My idea would be to do something along the lines of
n= size(x)%number of data points
numDivisions = 4;%number of times to divide the data
div = zeros(numDivisions,1)%number of points per division
p = zeros(numDivisions,4);% second number is degree of polynomial+1
S = zeros(numDivisions,1);
mu = zeros(numDivisions,1);
E = zeros(numDivisions,1);
for i = 1:numDivisions
div(i) = round(n(1,1)*i/numDivisions) %assign markers for divisions of points
end
for i = 1:size(div)
if i == 1
start = 1;
endpoint = div(i);
[p(i), S(i), mu(i)] = polyfit(x(start:endpoint), y(start:endpoint), 3);
else
[p(i), S(i), mu(i)] = polyfit(x(div(i-1):div(i)), y(div(i-1):div(i)), 3);
end
end
The goal would be to have an array of p values from the polyfits.
However, when I run it I get this error:
In an assignment A(I) = B, the number of elements in B
and I must be the same.
Error in (line 33)
[p(i), S(i), mu(i)] =
polyfit(x(start:endpoint),
y(start:endpoint), 3);
I want to auto-correlate a random noise vector with out any built-in MATLAB functions.
My auto correlation equation that is given is:
Rxx[L] = ∑ from n = 1 to N-1 [x(n)*x(n+L)]
L = [0:200]
I have written the code below but the plot Rxx vs L plot is not what I am expecting.
I am expecting my plot to start at some maximum at L = 0 or L = 1 since MATLAB starts its index at 1. Then exponentially decrease and saturates at a min of zero.
clc
clear all
randn('seed',2496132);
n = randn(1,1024);
upperbound = numel(n)-1;
for L = 1:200
for j = 1 : upperbound
n1(j) = n(j)+L;
Rxx(j) = (n(j)*n1(j));
end
Rxx_sum(L) = sum(Rxx);
Rxx = 0;
end
plot([1:200], Rxx_sum)
You have error in inner loop: you need to use n1(j) = n(j+L); instead n1(j) = n(j)+L;. E.g. you need add L to index instead value.
Second error is following: if you want to use upperbound = numel(n)-1 than you should use L equal to 0 or 1 only. E.g. you outer loop will be
for L = 0:1
...
Rxx_sum(L+1) = sum(Rxx);
...
Instead of this you can also correct upperbound value:
upperbound = numel(n) - maxL;
There maxL is maximal value of L that will used in next loop.
One more tip: it is possible to increase calculation speed if you replace inner loop with scalar product, e.g.
for L = 1:200
Rxx_sum(L) = n(1:upperbound) * n(1+L:upperbound+L)';
end
I ended up fixing my script with the help of the above code.
clc
clear all
randn('seed',2496132);
z = randn(1,1024);
n = [z zeros(1,200)];
upperbound = numel(z)-1;
for L = 0:200
for j = 1 : upperbound
Rxx(j) = (n(j)*n(j+L));
>end
Rxx_sum(L+1) = sum(Rxx);
Rxx = 0;
end
plot([0:200],Rxx_sum)
In matlab usually we add a header using fprintf command.
This is a problem when the size of the table depends on the input and when it exceeds a certain range (more than total number of column able to be presented in the command window).
When this occurs the header which we specified previously using the fprintf command will not be compatible with the current output data.
I would like to know is there a way like adding a character string into the 1st row of the matrix during some kind of iteration process. I had tried hardly but still can't find a proper way to solve this issue.
Or it is actually cannot be done in matlab for this purpose.
Eg
clear;clc
A = [2 8 3 1;0 2 -1 4;7 -2 1 2;-1 0 5 2]
B = [-2;4;3;5]
Es = 1e-5
n = length(B);
x = zeros(n,1);
Ea = ones(n,1);
iter = 0;
while max(Ea) >= Es
if iter <= 30
iter = iter + 1;
x_old = x;
for i = 1:n
j = 1:n;
j(i) = [];
x_cal = x;
x_cal(i) = [];
x(i) = (B(i) - sum(A(i,j) * x_cal)) / A(i,i);
end
else
break
end
x_ans(:,iter) = x;
Ea(:,iter) =abs(( x - x_old) ./ x);
end
result = [1:iter; x_ans; Ea]'
for the coding above..how could I add the heading like iteration for 1st column, x1...x2...x3..xn for nth column and error x1..error x2..error xn for another n column. I would like to make this heading can be automated generated based on the input matrix
If the size of the table depends on the input, use a cell array, using c = cell(...).
In each iteration simply call c{i,j} instead of c[i,j].