This is my first Matlab program.
I'm trying to use svmtrain and svmclassify with custom kernel.
Assume my kernel is regular inner product.
How should I write it?
I did:
function [K] = mykernel(U, V)
for i=size(U,1)
for j=size(V,1)
K(i,j) = dot(U(i,:),V(j,:));
end
end
return
end
and then in the command window:
x=randn(1000,10);
w=rand(1,10);
y=sign(x*w');
a=svmtrain(x,y,'kernel_function',mykernel);
and I get:
Error using mykernel (line 2)
Not enough input arguments.
Maybe one has a trick to do it without loops, something like U*V', it'll be nice to know this
trick, but i need to do it in loop, since i'm going to change the inner product to some more complicated stuff.
I also didn't really understand what are those U,V, and I didn't really get what this function
should return (is it the Gram matrix?)
Thanks for your help!!
--- EDIT:
I did the following:
function [K] = mink(U, V)
for i=1:size(U,1)
for j=1:size(V,1)
K(i,j) = min(exp(-dot(U(i,:),U(j,:))),exp(-dot(V(i,:),V(j,:))));
end
end
return
end
>>x=randn(100,10);
>>w=rand(1,10);
>>y=sign(x*w');
>>a=svmtrain(x,y,'kernel_function',#mink);
>>svmclassify(a, x)
Error using svmclassify (line 114)
An error was encountered during classification.
Attempted to access U(89,:); index out of bounds because size(U)=[88,10].
so now svmtrain works but svmclassify complains about size mismath (how did it get 88??)
In order to pass a function, you need to use the # symbol. This is shown in the docs, which quote:
#kfun — Function handle to a kernel function. A kernel function must be of the form
Bottom line, this will work.
a=svmtrain(x,y,'kernel_function',#mykernel);
Related
I'm newbie to Matlab
I have an assignment :
Legendre polynomial Pn(x), n=0,1,2,. . . The recursive formula of is
Write recursive sub-functions and non-recursive sub-functions separately to find the value of the Legendre polynomial function
This is my code :
function P =Legendre(n,x)
syms x;
n = input('n=');
if n==0
P=1;
elseif n==1
P=x;
elseif n>=2
P=((2*n-1)/n)*x*Legendre(n-1)-((n-1)/n)*Legendre(n-2);
end
end
But I get an error message:
Unrecognized function or variable 'Legendre'.
Error in ti4 (line 9)
P=((2*n-1)/n)*x*Legendre(n-1)-((n-1)/n)*Legendre(n-2);
Sorry for the stupid question. Can anyone help me? Thank u so much
A few things are probably going on here.
File name needs to match function name (for the primary function)
In your case, the filename needs to be Legendre.m.
Symbolic toolbox OR do you want an answer
for most uses of this function, I would leave two full inputs, just as you have them. Bur I would remove the first two lines completely.
As it is, the first two lines will break your inputs. The value for n is reset by the input function. I'm actually not sure what happens when you declare an existing variable x, to a sym.
Input consistency
You are setting up a function with two inputs, named n and x. But when you maek your recursive calls you only pass in one variable. The easiest thing to do here is simply keep passing n in as the first input.
(Right now, you are trying to pass in x in the recursive calls, but it will be interpreted as n.)
What is wrong with the following code?
clear all
syms x y a ;
u=2*x*y;
v=a^2+x^2-y^2;
diff=diff(u,'x',1)+diff(v,'y',1);
if diff==0
disp('Liquid motion is possible.')
disp('Stream function exists.')
else
disp('Liquid motion is not possible.')
disp('Stream function does not exist.')
end
diff2=diff(v,'x',1)-diff(u,'y',1);
if diff2==0
disp('Velocity potential exists.')
else
disp('Velocity potential does not exist.')
end
This comes in the command window when I run the above.
Liquid motion is possible.
Stream function exists.
Error using sym/subsindex (line 672)
Invalid indexing or function definition. When defining a function, ensure that the body of the function is a SYM
object. When indexing, the input must be numeric, logical or ':'.
Error in sym>privformat (line 1502)
x = subsindex(x)+1;
Error in sym/subsref (line 694)
[inds{k},refs{k}] = privformat(inds{k});
Error in q7 (line 17)
diff2=diff(v,'x',1)-diff(u,'y',1);
But if I rewrite(redefine) the symbolic variables after the first if construct, it runs fine. Also if I cancel the first if construct, it runs.
I would avoid to overwrite a reserved name, so instead of
diff=diff(u,'x',1)+diff(v,'y',1);
I would suggest
derFcn = diff(u,'x',1)+diff(v,'y',1);
This triggers the second error;
diff2=diff(v,'x',1)-diff(u,'y',1);
at this point diff is your diff value (which, incidentally is 0) so it is equivalent to write
0(v,'x',1)
which, of course, will not compile and it is not what you meant.
So, please, make the substitution (and update your if statements accordingly).
I have created a matlab GUI in which a user selects a variable to integrate with respect to, inputs the equation, and lower and upper limits. When my code goes to calculate the integral on pushbutton Callback, I get an error I don't understand.
This is the line of code causing the error:
i1 = int( eval(get(handles.edit1,'string')),
(handles.respectvar),
get(handles.edit3),
get(handles.edit2)
);
%respactvar is the user-selected variable, and edit3 and edit2 are the lower and upper limits.
And this is the error message:
Error using sym>tomupad (line 1135)
Conversion to 'sym' from 'struct' is not possible.
Error in sym (line 151)
S.s = tomupad(x);
Error in sym/int (line 142)
b = sym(b);
Error in projectCALC>pushbutton1_Callback (line 376)
i1=int(eval(get(handles.edit1,'string')),(handles.respectvar),get(handles.edit3),get(handles.edit2));
Error in gui_mainfcn (line 95)
feval(varargin{:});
Error in projectCALC (line 42)
gui_mainfcn(gui_State, varargin{:});
Error in #(hObject,eventdata)projectCALC('pushbutton1_Callback',hObject,eventdata,guidata(hObject))
Error while evaluating UIControl Callback
Thank you!
There are multiple problems with your code.
The first problem, as #excaza noted, is that you forgot to get the string property of the last two edit boxes, while you did this for the first one.
The second problem is that eval is very inefficient, and, in your case, very unsafe. What if somebody wrote a system() call into the editbox, erasing your hard drive?
The third problem is that even with eval or str2func, int requires its first argument to be a symbolic expression. This is a good thing: you don't actually have to use eval, you just have to convert your first string to a sym.
The fourth problem is that handles.respectvar also seems to be a GUI object, so you might need to get() some property for it in order to be able to use it as an integration variable.
Assuming that my suspicion is correct, and your edit1 contains a string like '3*x+y', edit2 and edit3 are limits such as '1' and '3', and handles.respectvar has a property that evaluates to 'x', then you should be calling
formula = sym(get(handles.edit1,'string'));
variable = handles.respectvar; %// more likely: get(handles.respectvar,...)
lim1 = str2double(get(handles.edit3,'string'));
lim2 = str2double(get(handles.edit2,'string'));
i1 = int(formula,variable,lim1,lim2);
A few notes:
Don't be afraid of using temporary variables where it helps in readability.
I converted the formula from sym to string, otherwise you get a warning or an error (depending on MATLAB version)
I left the order of lim1 <-> edit3, lim2 <-> edit2. Make sure this is indeed what you want, and orders are not reversed.
I converted the integration limits to double, but it seems that sym/int will also accept string input as the limit variables, so this is mostly for clarity.
I hope this is the right area. I'm trying to get this code to work in MatLab.
function y=test(x)
y=-x+(B/(B-1))*(r-a)*p+(B/(B-1))*(r-a)*(b((1-(b/x)^(B-1))/r- a)+p* ((b/x)^B))/(1-(b/x)^B);
end
I then jump to the command value and type this:
B=3.0515;
b=1.18632*10^5;
a=.017;
r=.054;
p=5931617;
I then try to find the zeros of the first equation by typing this and I get errors:
solution=fzero(#test,5000000)
I'm getting the following error:
Error: File: test.m Line: 5 Column: 1 This statement is not
inside any function. (It follows the END that terminates the
definition of the function "test".)
New error
Error using fzero (line 289)
FZERO cannot continue because user supplied function_handle ==> #(x)
(test(x,B,b,a,r,p))
failed with the error below.
Subscript indices must either be real positive integers or logicals.
I would guess that this is a problem of scoping, you are defining variables (B, b, etc...) in the command line but trying to use them inside your test function where they are out of scope. You should alter your test function to take these in as parameters and then use an anonymous function so that your call to test in fsolve still only takes a single parameter:
function y=test(x, B, b, r, a, p)
y=-x+(B/(B-1))*(r-a)*p+(B/(B-1))*(r-a)*(b((1-(b/x)^(B-1))/r- a)+p* ((b/x)^B))/(1-(b/x)^B);
end
and
B=3.0515;
b=1.18632*10^5;
a=.017;
r=.054;
p=5931617;
solution=fzero(#(x)(test(x,B,b,a,r,p)),5000000)
As an aside, unless you really do mean matrix multiplication, I would suggest that you replace all your *s and /s in test with the element-wise operators .* and ./. If you are dealing with scalars, it doesn't matter now, but it makes a big difference if you later want to scale your project and need a vectorized solution.
Regarding the errors you have added to your question:
You can't put code after the end in your function file. (With the exception of local functions). Your objective function should be an .m-file containing the code for one single function.
This is because in your test function you have ...b((1-(b/x)^(B-1))... which in MATLAB means you are trying to index the variable b in which case the value of (1-(b/x)^(B-1) has to be a positive integer. I'm guess you are missing a *
Your
function y=test(x)
y=-x+(B/(B-1))*(r-a)*p+(B/(B-1))*(r-a)*(b((1-(b/x)^(B-1))/r- a)+p* ((b/x)^B))/(1-(b/x)^B);
end
cannot access variables in your workspace. You need to pass the values in somehow. You could do something like:
function y=test(x,B,b,a,r,p)
y=-x+(B/(B-1))*(r-a)*p+(B/(B-1))*(r-a)*(b((1-(b/x)^(B-1))/r- a)+p* ((b/x)^B))/(1-(b/x)^B);
end
and then you can create an implicit wrapper function:
B=3.0515;
b=1.18632*10^5;
a=.017;
r=.054;
p=5931617;
solution = fzero(#(x) test(x,B,b,a,r,p),5000000)
I haven't tested whether fzero returns sensible results, but this code shouldn't give an error.
As part of a group project we have a system of 2 non linear differential equations and we have to draw the S=S(t) , I=I(t) graphic using the midpoint method.
And I'm getting the following error when trying to insert the matrix with the corresponding differential equations:
"Error in inline expression ==> matrix([[-(IS)/1000], [(IS)/1000 - (3*I)/10]])
Undefined function 'matrix' for input arguments of type 'double'.
Error in inline/subsref (line 23)
INLINE_OUT_ = inlineeval(INLINE_INPUTS_, INLINE_OBJ_.inputExpr, INLINE_OBJ_.expr);"
The code I have done is the following:
syms I S
u=[S;I];
F=[-0.001*S*I;0.001*S*I-0.3*I];
F1=inline(char(F),'I','S');
h=100; %Valores aleatórios
T=100000;
ni=(T/h);
u0=[799;1];
f=zeros(1,2);
k=zeros(1,2);
i=1;
while i<=ni
f(1)=F1(u0(1));
f(2)=F1(u0(2));
dx=h*f;
k(1)=F1((u0(1)+h*(1/2)),(u0(2)+h*(1/2)));
k(2)=F1((u0(1)+h*(1/2)),(u0(2)+h*(1/2)));
u1=u0+h*k;
disp('i:'),disp(i)
disp('u= '),disp(u1)
u0=u1;
i=i+1;
end
I'm new to this so the algorithm it's very likely to be wrong but if someone could help me with that error I'd apreciate it. Thank you!
The problem that specifically creates the error is that you are putting two symbolic functions into a matrix and then calling char (which outputs matrix([[-(IS)/1000], [(IS)/1000 - (3*I)/10]]) rather than converting nicely to string).
The secondary problem is that you are trying to pass two functions simultaneously to inline. inline creates a single function from a string (and using anonymous functions instead of inline is preferred anyway). You cannot put multiple functions in it.
You don't need sym here. In fact, avoid it (more trouble than it's worth) if you don't need to manipulate the equations at all. A common method is to create a cell array:
F{1} = #(I,S) -0.001*S*I;
F{2} = #(I,S) 0.001*S*I-0.3*I;
You can then pass in I and S as so:
F{1}(500,500)
Note that both your functions include both I and S, so they are always necessary. Reconsider what you were expecting when passing only one variable like this: f(1)=F1(u0(1));, because that will also give an error.