c******k
发帖数: 1140 | 1 -a*c*log(exp(-pi/(a*d))+exp(pi/(a*d)))+c*pi/d=0
其中
c=3.0e+8
d=345e-9
a的初始值在5.5e+5附近，但是用Matlab的fzero解这个单变量非线性方程，总是报如下
错误：
??? Error using ==> fzero
Function value at starting guess must be finite and real.
Error in ==> D:\NewData\Re-visite PBG Curve\FsolvePBGFun.m
On line 44 ==> x=fzero(inline('-x*(3.0e+8)*log(exp(-pi/(x*(345e-9))+exp(pi/
(x*(345e-9)))))+(3.0e+8)*pi/(345e-9)'),x0,options)；
a=5.5e+5的初始值，难道不是finite and real吗？换其它值也报错，怎么回事，谢谢
了 |
l*****i
发帖数: 3929 | 2 拜托请rescale一下你的方程，都出现e+17的系数了
pi/
【在 c******k 的大作中提到】
: -a*c*log(exp(-pi/(a*d))+exp(pi/(a*d)))+c*pi/d=0
: 其中
: c=3.0e+8
: d=345e-9
: a的初始值在5.5e+5附近，但是用Matlab的fzero解这个单变量非线性方程，总是报如下
: 错误：
: ??? Error using ==> fzero
: Function value at starting guess must be finite and real.
: Error in ==> D:\NewData\Re-visite PBG Curve\FsolvePBGFun.m
: On line 44 ==> x=fzero(inline('-x*(3.0e+8)*log(exp(-pi/(x*(345e-9))+exp(pi/
|
c******k
发帖数: 1140 | 3 如何调整，c 和 d 就是差别特别大
【在 l*****i 的大作中提到】
: 拜托请rescale一下你的方程，都出现e+17的系数了
:
: pi/
|
l*****i
发帖数: 3929 | 4 at least... divide both sides of your equation by c...
【在 c******k 的大作中提到】
: 如何调整，c 和 d 就是差别特别大
|
l*****i
发帖数: 3929 | 5 If you divide c on both sides of your equation, and do some simple math, reg
ard y=pi/(d*a), you will get a very simple equation:
log(exp(-y)+exp(y))-y = 0
Isn't this a very nicely scaled equation in y? Solve it using fzero you get
y = 20.48, then
a = pi/(20.48*d) = 4.4463e+5.
pi/
【在 c******k 的大作中提到】
: -a*c*log(exp(-pi/(a*d))+exp(pi/(a*d)))+c*pi/d=0
: 其中
: c=3.0e+8
: d=345e-9
: a的初始值在5.5e+5附近，但是用Matlab的fzero解这个单变量非线性方程，总是报如下
: 错误：
: ??? Error using ==> fzero
: Function value at starting guess must be finite and real.
: Error in ==> D:\NewData\Re-visite PBG Curve\FsolvePBGFun.m
: On line 44 ==> x=fzero(inline('-x*(3.0e+8)*log(exp(-pi/(x*(345e-9))+exp(pi/
|
c******k
发帖数: 1140 | 6 太感谢了，我咋这么笨呢
reg
get
【在 l*****i 的大作中提到】
: If you divide c on both sides of your equation, and do some simple math, reg
: ard y=pi/(d*a), you will get a very simple equation:
: log(exp(-y)+exp(y))-y = 0
: Isn't this a very nicely scaled equation in y? Solve it using fzero you get
: y = 20.48, then
: a = pi/(20.48*d) = 4.4463e+5.
:
: pi/
|
l*****i
发帖数: 3929 | 7 just found another thing: how did you get such a strange equation? If you do
what I told you to do, you get the equation in y, but it is equivalent to
exp(-y)+exp(y) = exp(y)
which does not have a solution at all! I suspect something in your original
equation was wrong...
【在 c******k 的大作中提到】
: 太感谢了，我咋这么笨呢
:
: reg
: get
|
c******k
发帖数: 1140 | 8 I already found this problem either. The good thing is that you give a hint
how to solve this kind of nonlinear equation. Actually I need solve two
nonlinear equations in one group, and there is another parameter b in the
above equation. For simplicity, I just let b=0.
do
original
【在 l*****i 的大作中提到】
: just found another thing: how did you get such a strange equation? If you do
: what I told you to do, you get the equation in y, but it is equivalent to
: exp(-y)+exp(y) = exp(y)
: which does not have a solution at all! I suspect something in your original
: equation was wrong...
|
l*****i
发帖数: 3929 | 9 all right, good luck then
hint
you
to
【在 c******k 的大作中提到】
: I already found this problem either. The good thing is that you give a hint
: how to solve this kind of nonlinear equation. Actually I need solve two
: nonlinear equations in one group, and there is another parameter b in the
: above equation. For simplicity, I just let b=0.
:
: do
: original
|
