mjhjmtu

I use this function:

documentclassstandalone
usepackagetikz
usepackagepgfplots
pgfplotssetcompat=1.15

 begindocument
 newcommandxmax14
 newcommandfmin(pi/3)
 newcommandfmax(2*pi)
 begintikzpicture
 [domain=xmax:0, samples=500]


 % The following line uses linear frequency increase
 %draw[ultra thick, red] plot (x, sin(deg((fmin+x*((fmax-fmin))/xmax)*x)) );
 % The following line uses exponential frequency increase
 draw[ultra thick, red] plot (x, sin(deg(exp(ln(fmin)+x/xmax*(ln(fmax)-ln(fmin)))*x)) );
 endtikzpicture
 enddocument

I need to evaluate the x parameter.
How can I print it's value?
also on log file is ok

Renato

To print all the points that the draw...plot is using, you can:

documentclassarticle
usepackagetikz
usepackagepgfplots
pgfplotssetcompat=1.15

begindocument
newcommandxmax14
newcommandfmin(pi/3)
newcommandfmax(2*pi)
begintikzpicture
 [domain=xmax:0, samples=500]
 draw[ultra thick, red] plot (x, sin(deg(exp(ln(fmin)+x/xmax*(ln(fmax)-ln(fmin)))*x)) );
endtikzpicture

pgfmathsetmacrostepxmax/500
foreach x in 0,step,...,xmax 
 x, qquad 
 pgfmathparsesin(deg(exp(ln(fmin)+x/xmax*(ln(fmax)-ln(fmin)))*x))pgfmathresult
 par


enddocument

(continuing...)

If you want the output on the log file, you can add (after the par, for example)

 wlogx is xspace and the function pgfmathresult 

and you'll have in your .log file:

x is 0 and the function 0.0
x is 0.028 and the function 0.02939
x is 0.056 and the function 0.05899
x is 0.084 and the function 0.08878
x is 0.112 and the function 0.11867

For the strange space, see Space after command with write

Clearly, to have it only on the log file, use as the loop:

foreach x in 0,step,...,xmax 
 pgfmathparsesin(deg(exp(ln(fmin)+x/xmax*(ln(fmax)-ln(fmin)))*x))
 wlogx is xspace and the function pgfmathresult 
 

You don't give us much information in your question, so I'm just using some dummy numbers....

documentclassarticle

usepackagetikz


begindocument

defx0.5
defxmax1
deffmin1
deffmax5


pgfmathparsesin(deg(exp(ln(fmin)+x/xmax*(ln(fmax)-ln(fmin)))*x))pgfmathresult


enddocument