File:2015arcDev.png

Deviation of the observed value of Russian rouble from the elliptic approximation Arc, versus time $x$.

Value of rouble is measured in the USA cents.

Time is measured in days since 2014.10.27.

The experimental data are taken from sites

https://www.mataf.net/en/currency/converter-USD-RUB (and are marked with blue dots) and from

www.cbr.ru/scripts/XML_dynamic.asp?date_req1=01/01/2014&date_req2=01/05/2015&VAL_NM_RQ=R01235 and are narked with black bars.

The Arc approximation is function

$\mathrm{Arc}(x)=0.01\sqrt{(a+x)(b−x)}~ ~$ $~$ with $~a=471~$ and $~b=123~$.

The experimental data are loaded as arrays of pairs $X_n,F_n$ for $n=1..N$; the marks at the graphic are centred at points

$y=F_n-\mathrm{Arc}(X_n)$