My graph is not picking up my time increments, its suppose to have a nice curve, but its coming out as a straight line.

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BAILEY MCMASTER
BAILEY MCMASTER 2023-9-25
评论： William Rose 2023-9-25
Ran in:
clear
Ts=30; % ms
Td=60; % ms
Chs=.001; % L/mmhg
Chd=.015; % L/mmhg
N=800; % number of elements
t=0:1:800; % all time values together
for i=0:N
if i<=99
Ch(i+1)=Chd; % starts at .015 L/mmhg in chd phase
elseif i>99 & i<=349
Ch(i+1)=(Chd-Chs)*exp((-t(i))/Ts)+Chs; % switches to chs
elseif i>349
Ch(i+1)=(Chs-Chd)*exp((-t(i))/Ts)+Chd; % switches back to chd
end
end
timebase=0:.01:8; % putting back in s
plot(timebase,Ch)
grid on
ylim([0 .02])
xlabel('time(s)')
ylabel('Ch (L/mmHg')
It's suppose to look like this.

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采纳的回答

William Rose
William Rose 2023-9-25
Ran in:
@BAILEY MCMASTER,
clear
Ts=30; % ms
Td=60; % ms
Chs=.001; % L/mmhg
Chd=.015; % L/mmhg
N=800; % number of elements
t=0:1:800; % all time values together
for i=0:N
if i<=99
Ch(i+1)=Chd; % starts at .015 L/mmhg in chd phase
elseif i>99 & i<=349
Ch(i+1)=(Chd-Chs)*exp(-(t(i)-99)/Ts)+Chs; % switches to chs
elseif i>349
Ch(i+1)=(Chs-Chd)*exp(-(t(i)-349)/Ts)+Chd; % switches back to chd
end
end
timebase=0:.01:8; % putting back in s
plot(timebase,Ch)
grid on
ylim([0 .02])
xlabel('time(s)')
ylabel('Ch (L/mmHg')
Good luck.
  5 个评论
显示 3更早的评论
William Rose
William Rose 2023-9-25
@BAILEY MCMASTER, you are welcome. The answer from @Star Strider is more elegant than my answer. @Star Strider's answer modifies your code in more significant ways. You and I can both learn from it.
William Rose
William Rose 2023-9-25
Ran in:
@BAILEY MCMASTER,
Your equation for the second phase (rising phase) does something which I suspect is not what you want: It starts the rising phase at Ch()=Chs. This is not a problem with the time constants and start times in this particular case, since the signal Ch() is very close to Chs before the rising phase begins. But what if the timing was such that Ch() had not yet decayed to Chs? With your current method, Ch() would instantly jump down to Chs, to begin its rising phase. That would be weird. See below, where I have changed Ts from 30 to 150 ms to illustrate my point.
clear
Ts=150; % 150 ms, not 30
Td=60; % ms
Chs=.001; % L/mmhg
Chd=.015; % L/mmhg
N=800; % number of elements
t=0:1:800; % all time values together
for i=0:N
if i<=99
Ch(i+1)=Chd; % starts at .015 L/mmhg in chd phase
elseif i>99 & i<=349
Ch(i+1)=(Chd-Chs)*exp(-(t(i)-99)/Ts)+Chs; % switches to chs
elseif i>349
Ch(i+1)=(Chs-Chd)*exp(-(t(i)-349)/Ts)+Chd; % switches back to chd
end
end
timebase=0:.01:8; % putting back in s
plot(timebase,Ch)
grid on
ylim([0 .02])
xlabel('time(s)')
ylabel('Ch (L/mmHg')
A better approach is to have Ch() begin its rising phase from whatever value it currently has.

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更多回答（1 个）

Star Strider
Star Strider 2023-9-25
Ran in:
Vectorised version —
clear
Ts=30; % ms
Td=60; % ms
Chs=.001; % L/mmhg
Chd=.015; % L/mmhg
N=800; % number of elements
t=0:1:800; % all time values together
Lv1 = t<=99;
Ch(Lv1) = Chd;
Lv2 = t>99 & t<=349;
Ch(Lv2) = (Chd-Chs)*exp(-t(1:nnz(Lv2))/Ts)+Chs; % switches to chs
Lv3 = t > 349;
Ch(Lv3) = (Chs-Chd)*exp(-t(1:nnz(Lv3))/Ts)+Chd; % switches back to chd
timebase=0:.01:8; % putting back in s
plot(timebase,Ch)
grid on
ylim([0 .02])
xlabel('time(s)')
ylabel('Ch (L/mmHg')
.

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