trigonometry question:how to change frequency

Question

I would change the formula that let this TiKZ function to draw frequency wave.

\documentclass{standalone}

\usepackage{tikz}

\usepackage{pgfplots}

\pgfplotsset{compat=1.15}

\begin{document}

    \newcommand{\xmax}{14}
    \newcommand{\fmin}{(pi/3)}
    \newcommand{\fmax}{(2*pi)}
\begin{tikzpicture}[domain=0:\xmax, samples=500]

    \draw[ultra thick, red] plot (\x, {sin(deg(exp(ln(\fmin)+\x/\xmax*(ln(\fmax)-ln(\fmin)))*\x))} );

\end{tikzpicture}
\end{document}

I think I understand how it works. But I still can't obtain the result I would.

I think, the draw function

\draw[ultra thick, red] plot (\x, {sin(deg(exp(ln(\fmin)+\x/\xmax*(ln(\fmax)-ln(\fmin)))*\x))} );

can draw the wave without a cycle (foreach or similar), because the \begin{tikzpicture}[domain=0:\xmax, samples=500] parameters (domain= 0:\xmax) tell to the \begin{tikzpicture} to repeat the \draw from o to \xmax

But, I'm not able to change the \draw to obtain an image that start from hight frequency to low.

I don't understand the trigonometric funcion.

Can someone help me to modify this function to obtain that?

no, I do not have sketch. But, I will prefer to obtain result with Latex. Can you give me link to sketch? — RenatoP, Dec 17 '18 at 14:54
Sorry cavern I did't understand well you question before. You can see the image that I want, compiling the code before. But inverted. Hight frequency before, low frequency then — RenatoP, Dec 17 '18 at 18:22

samcarter_is_at_topanswers.xyz · Accepted Answer · 2018-12-18T16:37:10.830

2

As long as there is no text etc. simply use xscale=-1 to invert left and right

\documentclass{standalone}

\usepackage{tikz}

\usepackage{pgfplots}

\pgfplotsset{compat=1.15}

\begin{document}

    \newcommand{\xmax}{14}
    \newcommand{\fmin}{(pi/3)}
    \newcommand{\fmax}{(2*pi)}
\begin{tikzpicture}[domain=0:\xmax, samples=500,xscale=-1]

    \draw[ultra thick, red] plot (\x, {sin(deg(exp(ln(\fmin)+\x/\xmax*(ln(\fmax)-ln(\fmin)))*\x))} );

\end{tikzpicture}
\end{document}

If you can use the axis environment from pgfplots, you can also reverse the direction of the x axis:

\documentclass{standalone} 
\usepackage{pgfplots}

\begin{document}

  \begin{tikzpicture}
    \begin{axis}[
      samples=1000,
      x dir=reverse,
      hide axis
    ]
      \addplot[domain=0:14] (x, {sin(deg(exp(ln((pi/3))+x/14*(ln((2*pi))-ln((pi/3))))*x))} );

    \end{axis}
  \end{tikzpicture}

\end{document}

(Needs pgfplots > 1.3)

edited Dec 18 '18 at 16:37

answered Dec 18 '18 at 10:44

samcarter_is_at_topanswers.xyz

158,329

nice answer, however this is tikz trick which draw mirror of defined function. correct solution is that op define new function with desired property. but this is not tikz problem ... – Zarko Dec 18 '18 at 11:11
@Zarko Feel free to add the correct solution as an answer :) – samcarter_is_at_topanswers.xyz Dec 18 '18 at 11:32
no, defining function is task of op (it is math task, not latex), not mine nor yours :-) – Zarko Dec 18 '18 at 11:56
oh, before i only write "nice answer" and forgot on +1. corrected now :-) – Zarko Dec 18 '18 at 13:49
@RenatoP ?????? – samcarter_is_at_topanswers.xyz Dec 19 '18 at 20:39
beautifull! last question: is it possible to have this waves, from lower to hight? – RenatoP Dec 19 '18 at 20:46
@RenatoP Isn't this exactly what the code in your question does? From low to high frequency? [I guess now I'm totally confused about what you are trying to achieve...] – samcarter_is_at_topanswers.xyz Dec 19 '18 at 20:48
@RenatoP Some of the regular user of your chat room (https://chat.stackexchange.com/rooms/41/tex-latex-and-friends) speak Italian. If you think it would be easier for you explain your problem in Italian, maybe you could ask them to help translate it. – samcarter_is_at_topanswers.xyz Dec 19 '18 at 20:53
yes, it does this, but I would like that: the higher frequency waves are "shorter" (or smaller) while, the lower frequency waves are talle (bigger). have I confused you more? – RenatoP Dec 19 '18 at 20:57
thank you smarter, the first problem is the concept. For me is not simple to explain neither in italian nor in english – RenatoP Dec 19 '18 at 21:01
@RenatoP That sounds exactly like the 4th solution by our tikz wizard marmot https://tex.stackexchange.com/a/464665/36296 – samcarter_is_at_topanswers.xyz Dec 19 '18 at 21:03
yes, but the waves must have a high to low frequency. – RenatoP Dec 19 '18 at 21:14
@RenatoP Sorry, I'm totally confused now. Can you take pen and paper and draw the image exactly like you want it to be? – samcarter_is_at_topanswers.xyz Dec 19 '18 at 21:18
Let us continue this discussion in chat. – RenatoP Dec 19 '18 at 21:23

trigonometry question:how to change frequency

1 Answers1