Find value of x from curve
조회 수: 1 (최근 30일)
이전 댓글 표시
hi, i had values of y from 0 to 2pi, related to x values from 0 to 10 with step 0.5; i.e., i calculated the value of y using program for the values of x=0:0.5:10. i want to find the value of x from the plot(x,y), for cer
x=0:0.5:10;
y=0 0.383135237593798 0.762305633253970 1.12500381866696 1.47841592230188 1.82360426305799 2.16799972102249 2.50162151353647 2.83129834831420 3.15388959500014 3.47113990999891 3.77183336056194 4.06431023145887 4.35173946610087 4.63997932479654 4.92354827732318 5.20849294256939 5.49434987763603 5.77926587166893 5.77926587166893 6.28318530717959
find x for values of y=0 1.57079632679490 3.14159265358979 4.71238898038469;
thanks a lot for any helps
댓글 수: 0
채택된 답변
Star Strider
2014년 12월 1일
편집: Star Strider
2014년 12월 1일
Use interp1, interpolating on the y values, reversing the x and y arguments. Your data contain two identical y-values, so it is necessary to cheat a bit and add a very small value (I chose 1E-15) to make them monotonically increasing in y. I sorted them first to be certain I wasn’t missing any of the repeated values:
x = 0:0.5:10;
y = [0 0.383135237593798 0.762305633253970 1.12500381866696 1.47841592230188 1.82360426305799 2.16799972102249 2.50162151353647 2.83129834831420 3.15388959500014 3.47113990999891 3.77183336056194 4.06431023145887 4.35173946610087 4.63997932479654 4.92354827732318 5.20849294256939 5.49434987763603 5.77926587166893 5.77926587166893 6.28318530717959];
yq = [0 1.57079632679490 3.14159265358979 4.71238898038469]; % Query Points
xy = [x' y']; % Create MAtrix For Sorting
[xys, idx] = sortrows(xy,2); % Sort
dup = find(diff([xys(:,2)]) == 0)+1; % Find Non-Increasing Values
xys(dup,2) = xys(dup,2) + [1:length(dup)]*1E-15; % Add ‘1E-15’ To Duplicates
xq = interp1(xys(:,2), xys(:,1), yq); % Interpolate To Find ‘x’ Values
figure(1)
plot(x, y, 'g')
hold on
plot(xq, yq, 'mp')
hold off
The ‘xq’ variable holds the x values you want that correspond to the y values in ‘yq’. The plot shows them.
추가 답변 (0개)
참고 항목
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!