Clear Filters
Clear Filters

how to linear interpolate using a for loop

2 views (last 30 days)
say I have a y = x^2 -2;
I want to find out which point of x it crosses y = 0 by linear interpolating. But by showing when the result flipes its signs. (meaning once we narrow out interpolation towards y=0, bottom side of y should be - and top portion of y should be +).Then narrow down until i get y = 0. How would I be able to use linear internpolation to find the exact data when y = 0?
I am getting some suggestion using a for loop. could you please show me an sample code how to linear internpolate such case?

Accepted Answer

Star Strider
Star Strider on 6 Oct 2021
x = linspace(-50, 50, 250);
y = x.^2 -2;
zx = find(diff(sign(y)))
zx = 1×2
121 129
for k = 1:numel(zx)
idxrng = max(1,zx(k))-2 : min(zx(k)+2, numel(x));
xi(k) = interp1(y(idxrng), x(idxrng), 0);
fprintf('x(y=0) = %10.6f\n', xi)
x(y=0) = -1.413163 x(y=0) = 1.413163
plot(x, y)
hold on
plot(xi, zeros(size(xi)), 'xr', 'MarkerSize',15)
hold off
This is a representative approach to this sort of problem.

More Answers (0)


Find more on Interpolation in Help Center and File Exchange




Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!