Calculating a time duration from the graph
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Hello
I am interested in finding out the time between two points in a graph (x-axis is the time, y-axis is the quantity of interest). For testing my logic, I'm using a sinusoidal wave to see if I get the correct responses. In the sinusoidal wave defined below, I'm interested in calculating the starting and ending x-coordinate when the y-axis value is less than 0.4.
t= [0:0.1:2*pi];
a=sin(t);
figure;
h=plot(t,a);
for i=1:max(t)
y=get(h,'ydata');
if a < 0.4
start=get(h,'xdata');
if a > 0.4
fin=get(h,'xdata');
end
end
This is an infinite loop, which doesn't give any output. I'm not really familiar with matlab and am not able to figure out how to get the start and fin values above.
Any help is appreciated.
Thanks!
采纳的回答
KSSV
2016-6-29
t= [0:0.1:2*pi];
a=sin(t);
figure;
h=plot(t,a);
% Get y data
y=get(h,'ydata');
% get x data
x=get(h,'xdata');
% find indices less then 0.4 in y
idx = find(y<0.4) ;
% get values of y less then 0.4
y1 = y(idx) ;
% get time for respective y values
x1 = x(idx) ;
% min time of 0.4
xmin = min(x1)
% max time of 0.4
xmax = max(x)
更多回答（1 个）
Aleksandra Ksiezyk
2020-1-20
0 个投票
hallo,
I came across this post because I am looking for something similar.
do you know how one can calculate the length of the x axis (or a curve) for a given condition? e.g. idx = find (y <0.4 & y> 0.3). I have a plot describing the temperature of time (24h) and I would like to calculate how much time during the day the temperature is from 17.5 to 18.5 C?
cheers,
Ola
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