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  • Users: mapi
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  1. mapi

    gray color for bar in the bar plot

    Thanks. I am reading it.
  2. mapi

    gray color for bar in the bar plot

    Hi, How to plot gray color for a set of bars and white color for another set of bars? And also, how to put legend on? Thanks, mapi
  3. mapi

    one-way anova with non-integral DOF

    I have group mean, 95% uncertainty (not std) and degrees of freedom (not integral) for each group. How do I compare the means? It seems that anova1 is not applicable. Thanks.
  4. mapi

    when capacitance depends on voltage, how to calculate impedance

    It is nonlinear, but we may approximate it with a linear curve, though not very good. Thanks.
  5. mapi

    when capacitance depends on voltage, how to calculate impedance

    Skogsgurra, Yes, the tube is soft, not infinitely stiff. So the tube will expand as pressure increases.
  6. mapi

    when capacitance depends on voltage, how to calculate impedance

    Thank you a lot. I(t)=dq/dt=d[C*V]/dt, I think we should put C(v(t)) into the derivative sign. For non-linear capacitance (not LTI system), I didn't know we can't transform it and get the impedance. My problem is this impedance, maybe it is not correct to obtain it just like LTI system: in...
  7. mapi

    when capacitance depends on voltage, how to calculate impedance

    Thanks for you questions. Yes, it is a mechanical system and I try to use circuit to simply the problem. So capacitance for example is C(V)=a*exp(-b*V)--a and b are constants. So C depends on the magnitude actually. voltage V(t) is not purely sinusoidal, but is periodic and has complex shape...
  8. mapi

    when capacitance depends on voltage, how to calculate impedance

    Thanks. we may say that the impedance I calculated in my last post is the impedance for that specific input, the pressure V(t).
  9. mapi

    when capacitance depends on voltage, how to calculate impedance

    Thank you all for your help. I think we may do it as: Given a voltage V(t), we can calculate the current through C(V).dV(t)/dt=I(t), then get the Fourier transform (FT) of V(t) and I(t), respectively. Now we calculate the impedance as: Z(w)=V(w)/I(W). Please correct me if there is any. Thanks.
  10. mapi

    when capacitance depends on voltage, how to calculate impedance

    BobM3, I asked some people in EE, they didn't say time-dependent impedance was wrong. For my problem, it is just a simplification of a tube with pressure inside, and so the compliance (capacitance) depends on pressure (voltage). Mapi
  11. mapi

    when capacitance depends on voltage, how to calculate impedance

    Bronzeado, Could you please give me the paper information if you know? Now I am concerned with the definition of impedance: voltage(t)/current(t) in time domain. If we want the impedance in the frequency domain, two methods: 1) FFT of voltage and current, then impedance is V(w)/I(w); 2)...
  12. mapi

    when capacitance depends on voltage, how to calculate impedance

    Unfortunately I do need this non-linear circuit, and try to see if such nonlinear circuit is better than linear circuit.
  13. mapi

    when capacitance depends on voltage, how to calculate impedance

    It is an analog: simply my current situation under study with a circuit. Then I need to calculate the impedance from circuit and fit it to the experimental data.
  14. mapi

    when capacitance depends on voltage, how to calculate impedance

    If just substitute equation of C into Z(w)=1/jWC, then Z(w) will be time-dependent, which seems not correct? In my case, capacitance is indeed dependent of voltage. When calculating impedance, do we do that in time domain or frequency domain? Complex V(t)/I(t) or V(w)/I(w)?
  15. mapi

    when capacitance depends on voltage, how to calculate impedance

    For a simple circuit with only one capacitor C, when C is constant, the impedance is Z(w)=1/jWC. But when C is dependent of the voltage, C(V), then what is the impedance? Thanks, Mapi
  16. mapi

    statistics on experimental results---need help

    Hi, Data A from group 1 and B from group 2. Now mean(A) is larger than mean(B). We want to compare the two groups: In Matlab, ttest2 is used: To test if A is greater than B: p=ttest2(A,B,0.05,'right') give p=0.045<0.05, so mean of A is statistically greater than mean of B. To test if...
  17. mapi

    the range in xlswrite function??

    xlswrite(filename, M, sheet, 'range') E.g., the 'range' can be 'B2:G5'. Can we rewrite the range as 'Bnum_1:Gnum_2', where num_1=2 and num_2=5? Thanks, Mapi
  18. mapi

    anybody know the difference between filter and filtfilt

    Thanks. I will read the help file carefully again. Mapi
  19. mapi

    anybody know the difference between filter and filtfilt

    Hi, I want to filter some experimental data: y=f(x),---smooth the y values. But I have tried both filter and filtfilt, what is the difference between them? Or which one is better? Mapi
  20. mapi

    about standard deviation in ttest

    Thanks. Just because my sample size is less than 5, I have to be very careful about it. mapi

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