# ECCONV is the jEllipse module of jLab.

``` ECCONV  Converts between eccentricity measures.

Y=ECCONV(X,STR) converts the eccentricity measure X into eccentricity
measure Y as specified by the string STR.

STR is of the form 'in2out' where the names 'in' and 'out' may be
chosen from the following table.

STR        Name                    Definition
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'ecc'       Eccentricity            sgn(b)*sqrt(1-b^2/a^2)
'ell'       Ellipticity             b/a
'lin'       Linearity               sgn(b)*(a^2-b^2)/(a^2+b^2)
'circ'      Circularity             2ab/(a^2+b^2)
'nu'        Eccentricity angle      asin(b/sqrt(a^2 + b^2))
'rot'       Rotary ratio            sgn(b)*(a-abs(b))/(a+abs(b))

where "a" and "b" are the semi-major and semi-minor axes respective.
For example, ECC=ECCONV(L,'lin2ecc') converts the ellipse linearity L
into eccentricity ECC.

All quantities are positive for mathematically positive rotation
and negative for mathematically negative rotation.  Note the linearity
is undefined for the case of purely circular rotation a=abs(b);

For further details, see Lilly and Gascard (2006).
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Cell array input/output

If ECCONV is given cell array input, it returns cell array output.

Thus X may be a cell arrays of numerical arrays, and the output Y will
also be a cell array having an identical size as X.
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