How to find when the value is 0 in an array?

Im plotting a graph of X against Y and i want to know the value of X when Y = 0. I have tried to use the find command and doing find(Y==0) but because in the array there is no exact zero number (goes to 0.00024 then to negative) it wont return anything.

Y = (U_y .* time) - (0.5 .* g .* (time).^2) + handles.Height;
Index = find(Y==0)
X_point = X(Index)

Answer 1

[Rik]

This answer contains code to find the zero crossing in a vector

https://www.mathworks.com/matlabcentral/answers/267222-easy-way-of-finding-zero-crossing-of-a-function#answer_209072

Answer 2

[Walter Roberson]

[~, Index] = min(abs(Y));

The zero crossing will be between the point at Index and the next point over in one of the two directions.

You could also use

mask = Y > 0;
% goes from positive to negative ?
Index = find(Y(1:end-1) & ~Y(2:end));
if isempty(Index); 
    % goes from negative to positive ?
    Index = find(~Y(1:end-1) & Y(2:end));
end
if isempty(Index)
    %no zero crossing
end

[Greg Simmons]

very clever!... this second script helped me a lot. Thanks Walter.

[Walter Roberson]

The script should probably be

mask = Y > 0;
% goes from positive to negative ?
Index = find(mask(1:end-1) & ~mask(2:end));
if isempty(Index); 
    % goes from negative to positive ?
    Index = find(~mask(1:end-1) & mask(2:end));
end
if isempty(Index)
    %no zero crossing
end