How to move quiver arrows within the semi-circle

x=0:0.01:1;

y=0:0.01:1;

x=x.^2

y=-x.*y

c=10

quiver(x(1:c:end),y(1:c:end))

hold on

y=-x+1

plot(x,y)

y=sqrt(1-x.^2)

plot(x,y)

xlim([0 12])

ylim([0 1])

This code gave me this plot.

However, I want to obtain a plot something like this:

Sorry for the bad explanation.

Is it possible to move the quiver arrows to fit in the semi-circle equation?

Answer 1

[Voss]

It's not clear how you determine where the quivers start, i.e., where the 'base' of each one (not the arrow end - the other end) belongs, so here they all start along the line y = 1:

x=0:0.01:1;
y=sqrt(1-x.^2);

c=10;
xq = x(1:c:end); % an arrow at each x
nq = numel(xq);
yq = ones(1,nq); % all starting along the line y = 1
uq = zeros(1,nq); % pointing straight down: u = zero (no x-component)
vq = y(1:c:end)-1; %                        v = y-1 (from the line y = 1 to the curve y = sqrt(1-x^2))

quiver(xq,yq,uq,vq,'AutoScale','off')

hold on
plot(x,1-x)
plot(x,y)

[Jong Hyun Lee]

Thank you for the answer. However, the plot that you obtained have vertical arrows not inclined. How can I use quiver function to plot inclined arrows?

The quiver starts at y=1

[Voss]

Here are some inclined arrows starting at y=1:

x=0:0.01:1;
y=sqrt(1-x.^2);

c=10;
xq = x(1+c:c:end);
nq = numel(xq);
yq = ones(1,nq);

uq = x(1:c:end-c)-xq;
vq = y(1:c:end-c)-1;

quiver(xq,yq,uq,vq,'AutoScale','off')

hold on
plot(x,1-x)
plot(x,y)