plotting multiple function on octave. I already looked for an answer but something is not working
Let f be a continuous real function defined on the interval [a,b]. I want to aproximate this function by a piecewise quadratic polynomial. I already created a matrix that summarizes these polynomials. Let's say that I'm considering a uniform partition of the interval into N pieces ( therefore N+1 points).
I have a matrix A of size N times 3, where the k row represents the quadratic polynomial associated with the k-interval of this partition in the natural form ( the row [a b c] represents the polynomial a+bx+cx^2). I already created a method to find this matrix (obviously it depends on the choice of my interpolation points inside of each interval but that it doesn't matter for this question).
I'm trying to plot the corresponding function but I'm having some problems. I used the same idea given in Similar question. This is what I wrote
x=zeros(N+1,1);
%this is the set of points defining the uniform partition
for i=1:N+1
x(i)=a+(i-1)*((b-a)/(N));
end
%this is the length of my linspace for plotting the functions
l=100
And now I plot the functions:
figure;
hold on;
%first the original function
u=linspace(a,b,l*N);
v=arrayfun( f , u);
plot(u,v,'b')
% this is for plotting the other functions
for k=1:N
x0=linspace(x(k),x(k+1));
y0=arrayfun(@(t) [1,t,t^2]*A(k,:)',x0);
plot(x0, y0, 'r');
end
The problem is that the for is plotting the same function f and I don't know why. I tried with multiple different functions. I'm pretty sure that my matrix A is correct.
plot octave piecewise
asked Nov 12 '18 at 18:04
CarvalCarval
12
add a comment |
Let f be a continuous real function defined on the interval [a,b]. I want to aproximate this function by a piecewise quadratic polynomial. I already created a matrix that summarizes these polynomials. Let's say that I'm considering a uniform partition of the interval into N pieces ( therefore N+1 points).
I have a matrix A of size N times 3, where the k row represents the quadratic polynomial associated with the k-interval of this partition in the natural form ( the row [a b c] represents the polynomial a+bx+cx^2). I already created a method to find this matrix (obviously it depends on the choice of my interpolation points inside of each interval but that it doesn't matter for this question).
I'm trying to plot the corresponding function but I'm having some problems. I used the same idea given in Similar question. This is what I wrote
x=zeros(N+1,1);
%this is the set of points defining the uniform partition
for i=1:N+1
x(i)=a+(i-1)*((b-a)/(N));
end
%this is the length of my linspace for plotting the functions
l=100
And now I plot the functions:
figure;
hold on;
%first the original function
u=linspace(a,b,l*N);
v=arrayfun( f , u);
plot(u,v,'b')
% this is for plotting the other functions
for k=1:N
x0=linspace(x(k),x(k+1));
y0=arrayfun(@(t) [1,t,t^2]*A(k,:)',x0);
plot(x0, y0, 'r');
end
The problem is that the for is plotting the same function f and I don't know why. I tried with multiple different functions. I'm pretty sure that my matrix A is correct.
plot octave piecewise
asked Nov 12 '18 at 18:04
CarvalCarval
12
Have you tried to puthold offat the end?
– Michael O.
Nov 12 '18 at 22:53
add a comment |
Let f be a continuous real function defined on the interval [a,b]. I want to aproximate this function by a piecewise quadratic polynomial. I already created a matrix that summarizes these polynomials. Let's say that I'm considering a uniform partition of the interval into N pieces ( therefore N+1 points).
I have a matrix A of size N times 3, where the k row represents the quadratic polynomial associated with the k-interval of this partition in the natural form ( the row [a b c] represents the polynomial a+bx+cx^2). I already created a method to find this matrix (obviously it depends on the choice of my interpolation points inside of each interval but that it doesn't matter for this question).
I'm trying to plot the corresponding function but I'm having some problems. I used the same idea given in Similar question. This is what I wrote
x=zeros(N+1,1);
%this is the set of points defining the uniform partition
for i=1:N+1
x(i)=a+(i-1)*((b-a)/(N));
end
%this is the length of my linspace for plotting the functions
l=100
And now I plot the functions:
figure;
hold on;
%first the original function
u=linspace(a,b,l*N);
v=arrayfun( f , u);
plot(u,v,'b')
% this is for plotting the other functions
for k=1:N
x0=linspace(x(k),x(k+1));
y0=arrayfun(@(t) [1,t,t^2]*A(k,:)',x0);
plot(x0, y0, 'r');
end
The problem is that the for is plotting the same function f and I don't know why. I tried with multiple different functions. I'm pretty sure that my matrix A is correct.
plot octave piecewise
asked Nov 12 '18 at 18:04
CarvalCarval
12
Let f be a continuous real function defined on the interval [a,b]. I want to aproximate this function by a piecewise quadratic polynomial. I already created a matrix that summarizes these polynomials. Let's say that I'm considering a uniform partition of the interval into N pieces ( therefore N+1 points).
I have a matrix A of size N times 3, where the k row represents the quadratic polynomial associated with the k-interval of this partition in the natural form ( the row [a b c] represents the polynomial a+bx+cx^2). I already created a method to find this matrix (obviously it depends on the choice of my interpolation points inside of each interval but that it doesn't matter for this question).
I'm trying to plot the corresponding function but I'm having some problems. I used the same idea given in Similar question. This is what I wrote
x=zeros(N+1,1);
%this is the set of points defining the uniform partition
for i=1:N+1
x(i)=a+(i-1)*((b-a)/(N));
end
%this is the length of my linspace for plotting the functions
l=100
And now I plot the functions:
figure;
hold on;
%first the original function
u=linspace(a,b,l*N);
v=arrayfun( f , u);
plot(u,v,'b')
% this is for plotting the other functions
for k=1:N
x0=linspace(x(k),x(k+1));
y0=arrayfun(@(t) [1,t,t^2]*A(k,:)',x0);
plot(x0, y0, 'r');
end
The problem is that the for is plotting the same function f and I don't know why. I tried with multiple different functions. I'm pretty sure that my matrix A is correct.
plot octave piecewise
plot octave piecewise
asked Nov 12 '18 at 18:04
CarvalCarval
12
asked Nov 12 '18 at 18:04
CarvalCarval
12
asked Nov 12 '18 at 18:04
CarvalCarval
12
asked Nov 12 '18 at 18:04
CarvalCarval
12
asked Nov 12 '18 at 18:04
CarvalCarval
12
12
Have you tried to puthold offat the end?
– Michael O.
Nov 12 '18 at 22:53
add a comment |
Have you tried to puthold offat the end?
– Michael O.
Nov 12 '18 at 22:53
Have you tried to put
hold off at the end?– Michael O.
Nov 12 '18 at 22:53
Have you tried to put
hold off at the end?– Michael O.
Nov 12 '18 at 22:53
add a comment |
1 Answer
1
active
oldest
votes
Please write a minimal working example that can be run as standalone code or copy/pasted from people here to check where you might have a bug -- often in the process of reducing your code to its bare principles in this manner, you end up figuring out what is the problem yourself in the first place. But, in any case, I have written one myself and cannot replicate the problem.
figure;
hold on;
# arbitrary values for Minimal Working Example
N = 10;
x = [10:10:110]; # (N+1, 1)
A = randn( N, 3 ); # (3 , N)
a = 100; b = 200; l = 3;
f = @(t) t.^2 .* sin(t);
%first the original function
u = linspace(a,b,l*N);
v = arrayfun( f , u);
plot(u,v,'b')
for k = 1 : N
x0 = linspace( x(k), x(k+1) )
y0 = arrayfun( @(t) ([1, t, t.^2]) * (A(k, :).'), x0 )
x0, y0
plot(x0, y0, 'r');
endfor
hold off;
Output:
Are you doing something different?
answered Nov 13 '18 at 18:39
Tasos PapastylianouTasos Papastylianou
10.8k1932
add a comment |
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1 Answer
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active
oldest
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1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
Please write a minimal working example that can be run as standalone code or copy/pasted from people here to check where you might have a bug -- often in the process of reducing your code to its bare principles in this manner, you end up figuring out what is the problem yourself in the first place. But, in any case, I have written one myself and cannot replicate the problem.
figure;
hold on;
# arbitrary values for Minimal Working Example
N = 10;
x = [10:10:110]; # (N+1, 1)
A = randn( N, 3 ); # (3 , N)
a = 100; b = 200; l = 3;
f = @(t) t.^2 .* sin(t);
%first the original function
u = linspace(a,b,l*N);
v = arrayfun( f , u);
plot(u,v,'b')
for k = 1 : N
x0 = linspace( x(k), x(k+1) )
y0 = arrayfun( @(t) ([1, t, t.^2]) * (A(k, :).'), x0 )
x0, y0
plot(x0, y0, 'r');
endfor
hold off;
Output:
Are you doing something different?
answered Nov 13 '18 at 18:39
Tasos PapastylianouTasos Papastylianou
10.8k1932
add a comment |
Please write a minimal working example that can be run as standalone code or copy/pasted from people here to check where you might have a bug -- often in the process of reducing your code to its bare principles in this manner, you end up figuring out what is the problem yourself in the first place. But, in any case, I have written one myself and cannot replicate the problem.
figure;
hold on;
# arbitrary values for Minimal Working Example
N = 10;
x = [10:10:110]; # (N+1, 1)
A = randn( N, 3 ); # (3 , N)
a = 100; b = 200; l = 3;
f = @(t) t.^2 .* sin(t);
%first the original function
u = linspace(a,b,l*N);
v = arrayfun( f , u);
plot(u,v,'b')
for k = 1 : N
x0 = linspace( x(k), x(k+1) )
y0 = arrayfun( @(t) ([1, t, t.^2]) * (A(k, :).'), x0 )
x0, y0
plot(x0, y0, 'r');
endfor
hold off;
Output:
Are you doing something different?
answered Nov 13 '18 at 18:39
Tasos PapastylianouTasos Papastylianou
10.8k1932
add a comment |
Please write a minimal working example that can be run as standalone code or copy/pasted from people here to check where you might have a bug -- often in the process of reducing your code to its bare principles in this manner, you end up figuring out what is the problem yourself in the first place. But, in any case, I have written one myself and cannot replicate the problem.
figure;
hold on;
# arbitrary values for Minimal Working Example
N = 10;
x = [10:10:110]; # (N+1, 1)
A = randn( N, 3 ); # (3 , N)
a = 100; b = 200; l = 3;
f = @(t) t.^2 .* sin(t);
%first the original function
u = linspace(a,b,l*N);
v = arrayfun( f , u);
plot(u,v,'b')
for k = 1 : N
x0 = linspace( x(k), x(k+1) )
y0 = arrayfun( @(t) ([1, t, t.^2]) * (A(k, :).'), x0 )
x0, y0
plot(x0, y0, 'r');
endfor
hold off;
Output:
Are you doing something different?
answered Nov 13 '18 at 18:39
Tasos PapastylianouTasos Papastylianou
10.8k1932
Please write a minimal working example that can be run as standalone code or copy/pasted from people here to check where you might have a bug -- often in the process of reducing your code to its bare principles in this manner, you end up figuring out what is the problem yourself in the first place. But, in any case, I have written one myself and cannot replicate the problem.
figure;
hold on;
# arbitrary values for Minimal Working Example
N = 10;
x = [10:10:110]; # (N+1, 1)
A = randn( N, 3 ); # (3 , N)
a = 100; b = 200; l = 3;
f = @(t) t.^2 .* sin(t);
%first the original function
u = linspace(a,b,l*N);
v = arrayfun( f , u);
plot(u,v,'b')
for k = 1 : N
x0 = linspace( x(k), x(k+1) )
y0 = arrayfun( @(t) ([1, t, t.^2]) * (A(k, :).'), x0 )
x0, y0
plot(x0, y0, 'r');
endfor
hold off;
Output:
Are you doing something different?
answered Nov 13 '18 at 18:39
Tasos PapastylianouTasos Papastylianou
10.8k1932
answered Nov 13 '18 at 18:39
Tasos PapastylianouTasos Papastylianou
10.8k1932
answered Nov 13 '18 at 18:39
Tasos PapastylianouTasos Papastylianou
10.8k1932
answered Nov 13 '18 at 18:39
Tasos PapastylianouTasos Papastylianou
10.8k1932
10.8k1932
add a comment |
add a comment |
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Have you tried to put
hold offat the end?– Michael O.
Nov 12 '18 at 22:53