Error Bars Logarithmic
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Logarithmic Error Calculation
software MathWorks Support Team (view profile) 13,593 questions 13,593 answers 13,592 accepted answers Reputation: 2,574 Vote0 How can I use the ERRORBAR function with a logarithmic axis in MATLAB? Asked by MathWorks Support Team MathWorks Support Team (view profile) 13,593 questions 13,593 answers 13,592 accepted answers Reputation: 2,574 on 27 Jun 2009 uncertainty logarithm base 10 Latest activity Commented on by Ohad BarSimanTov Ohad BarSimanTov (view profile) 0 questions 0 answers 0 accepted answers Reputation: 0 on 27 Jul 2016 Accepted Answer by MathWorks Support Team MathWorks Support Team (view profile) 13,593 questions 13,593 answers 13,592 accepted answers Reputation: 2,574 227 views (last 30 days) 227 views (last 30 days) When I type the following at the MATLAB prompt, I get a an errorbar with a log x axis:x = 1:100; y = sin(x); e = std(y)*ones(size(x)); errorbar(x,y,e) set(gca,'xscale','log') However, the errorbars of the first point in the resulting figure extend much farther than the other errorbars. I would like a function that can account for the logrithmic X-axis and make all of the errorbars have a uniform width. 1 Comment Show all comments Ohad BarSimanTov Ohad BarSimanTov (view profile) 0 questions 0 answers 0 accepted answers Reputation: 0 on 27 Jul 2016 Direct link to this comment: https://www.mathworks.com/matlabcentral/answers/99844#comment_381798 This is
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a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and http://physics.stackexchange.com/questions/95254/the-error-of-the-natural-logarithm policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Physics Questions Tags Users Badges Unanswered Ask Question _ Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Join them; it only takes a minute: Sign error bars up Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top The error of the natural logarithm up vote 10 down vote favorite 2 Can anyone explain why the error for $\ln (x)$ (where for $x$ we have $x\pm\Delta x$) is simply said to be $\frac{\Delta error bars on x}{x}$? I would very much appreciate a somewhat rigorous rationalization of this step. Additionally, is this the case for other logarithms (e.g. $\log_2(x)$), or how would that be done? error-analysis share|cite|improve this question edited Jan 25 '14 at 20:01 Chris Mueller 4,72711444 asked Jan 25 '14 at 18:31 Just_a_fool 3341413 add a comment| 2 Answers 2 active oldest votes up vote 17 down vote accepted Simple error analysis assumes that the error of a function $\Delta f(x)$ by a given error $\Delta x$ of the input argument is approximately $$ \Delta f(x) \approx \frac{\text{d}f(x)}{\text{d}x}\cdot\Delta x $$ The mathematical reasoning behind this is the Taylor series and the character of $\frac{\text{d}f(x)}{\text{d}x}$ describing how the function $f(x)$ changes when its input argument changes a little bit. In fact this assumption makes only sense if $\Delta x \ll x$ (see Emilio Pisanty's answer for details on this) and if your function isnt too nonlinear at the specific point (in which case the presentation of a result in the form $f(x) \pm \Delta f(x)$ wouldnt make sense anyway). No