drawing a point in the graph

Answer 1

[Arif Hoq]

x = 1:5;
y = 20:24;
plot(x,y,x(3),y(3),'*') % specify a marker symbol * in index 3 of y

please follow this for more information about plot

https://www.mathworks.com/help/matlab/ref/plot.html

[Ismita]

thank you. How can I mark the point of intersection in the following case?

"

t1 = 0:0.5:2;
x1 = t1/2-1;
t2 = 2:0.5:20;
x2 = t2 - sqrt(2*t2);
t3 = 0:0.5:1;
x3 = t3+1;
t4 = 1:0.5:11.6;
x4 = 2*sqrt(t4);

figure(1)
plot(x1, t1, 'b', x2, t2, 'r', x3, t3, 'k', x4, t4, 'g')

"

[Arif Hoq]

try this approach. I am not sure about his efficiency.

t1 = 0:0.5:2;
x1 = t1/2-1;
t2 = 2:0.5:20;
x2 = t2 - sqrt(2*t2);
t3 = 0:0.5:1;
x3 = t3+1;
t4 = 1:0.5:11.6;
x4 = 2*sqrt(t4);
figure(1)
[x1equality ia]=find(ismember(t1,t2));
[x3equality ib]=find(ismember(t3,t4));
plot(x1, t1, 'b', x2, t2, 'r', x3, t3, 'k', x4, t4, 'g',x1(ia),t1(ia),'*',x3(ib),t3(ib),'*')

[Ismita]

Thank you :)

Answer 2

[Walter Roberson]

x = 0:0.5:10;
t = (x/2).^2;

abs(x-2*sqrt(t))  %cross-check weether x == 2*sqrt(t)

ans = 1×21

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

plot(x, t, '*-')

[Ismita]

thank you. How can I mark the point of intersection in the following case? TIA

t1 = 0:0.5:2;
x1 = t1/2-1;
t2 = 2:0.5:20;
x2 = t2 - sqrt(2*t2);
t3 = 0:0.5:1;
x3 = t3+1;
t4 = 1:0.5:11.6;
x4 = 2*sqrt(t4);
figure(1)
plot(x1, t1, 'b', x2, t2, 'r', x3, t3, 'k', x4, t4, 'g')

[Walter Roberson]

You need to calculate the point of interesection between (x2,t2) and (x4,t4) . Then you can plot() that point, specifying a marker. For example,

plot(interesection_x, intersection_y, 'b*')

[Ismita]

Problem is, the point of intersection is only one point but the x and t limits are not from the same region (x1, x2, x3, x4 and corresponding t1, t2, t3, t4) plot. The intersection is x4==6.78233, t2==11.66

plot(x4==6.78233, t2==11.66,'r*') does not work

[Walter Roberson]

plot(6.78233, 11.66, 'r*')

It does not matter if there is no exact match for this in the curves, if it is the correct intersection point.

Unless, that is, what you want to do is find the closest point on each of the two curves and mark those close points rather than the intersection point?

[Ismita]

thank you :)