Find intersection of curve and line.

1 view (last 30 days)
A Akhilesh on 1 Apr 2021
Commented: Star Strider on 5 Apr 2021
i have two equations yw and y1 i need to find intersection of both line and curve and then find the distance of the point from origin. i have only points of y and x for making the curve and have used polynomial interpolation for that
clear
syms x1
x=[0;1;2;3];
y=[7;5;11;28];
for i=1:4
for j=1:4
a(i,j)=power(x(i),(j-1));
end
end
b=inv(a)*(y);
y1=b(1,1)+(b(2,1)*x1)+(b(3,1)*x1.^2)+(b(4,1)*x1.^3);
fplot(yw,[0,5])
hold onclc
fplot(y1,[0,5])

Star Strider on 1 Apr 2021
Try this:
syms x1
x=[0;1;2;3];
y=[7;5;11;28];
for i=1:4
for j=1:4
a(i,j)=power(x(i),(j-1));
end
end
b=inv(a)*(y);
y1=b(1,1)+(b(2,1)*x1)+(b(3,1)*x1.^2)+(b(4,1)*x1.^3);
xv = vpasolve(y1-yw==0,x1) % X-Value At Intersection
yv = subs(yw, x1, xv) % Y-Value At Intersection
figure
fplot(yw,[0,5])
hold on
fplot(y1,[0,5])
plot(double(xv), double(yv), '+r')
hold off
xlim([0 5])
legend('yw','y1','Intersection', 'Location','best')
.
A Akhilesh on 5 Apr 2021
Hey!, thanks for the answer. i would like to know if the same thing would work when i have n points defining my curve, which gives me an nth degree polynomial.
Star Strider on 5 Apr 2021
As always, my pleasure!
Calculating the intersections of lines defined by data (rather than expressions) from two different data sets is similar in concept, although the code differs. See Plot a point of intersection between 2 lines or curves for a typical approach.