Ode45 handles function error

2020 1 2
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更新时间：2020 1 2
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My function ug data is got from edittext of GUI
function ut = ug(handles, x, y)
ut = handles.edit11.String
evalc(ut)
vg is like that
Question: When i put the formula to the push button of gui below to get the dy/dx = ug/vg i got error
Formula: for a=-5:1:5;
tspan = [a 6];
y0 = [-5 5];
[xx,yy] = ode45(@(x,y) (vg(handles, x, y))./(ug(handles, x, y)), tspan, y0);
plot(xx,yy,'-k','linewidth',2);
hold on
end
My code works if i create a function like ut=ug(x,y) .... but if i do like that i cant get datas from edittext. How can i activate the code in ode 45 with datas in edit text??

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Walter Roberson
Walter Roberson 2020-1-2
You should be using str2func instead of evalc()
But you have a problem that you have a division by 0. Your first formula crosses 0 slightly above x =-1 and the time is included in all of your timespan for a = -5:-1. This is a problem because you are dividing by that.
esat gulhan
esat gulhan 2020-1-2
Well
I change the formula and limits like that.So div/0 is not problem, i erased evalc(ut) in the function and write
function ut = ugs(handles, x, y)
ut = handles.edit11.String
str2func(ut)
end, and rewrite vg too
Formula: for a=1:1:5; (limits changed)
tspan = [a 6];
y0 = [-5 5];
[xx,yy] = ode45(@(x,y) (vg(handles, x, y))./(ug(handles, x, y)), tspan, y0);
plot(xx,yy,'-k','linewidth',2);
hold on
Now it gives new error,
Error using odearguments (line 90)
@(X,Y)UG(HANDLES,X,Y) must return a column vector.
esat gulhan
esat gulhan 2020-1-2
But if i change code like that
[xx,yy] =ode45(@(x,y) (1.5-0.8*y)./(0.8*x+0.5) , tspan, y0)
it works, but my wish to take formulas from the edit text of gui. I dont want to write all time manuel to the formula.

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