## Fitting an ellipse

Ax^2 +Bxy+Cy^2+Dx+Ey+F=0, if B^2-4AC<0

The trick is the use of the conditional calculation of y(x) depending on the value of the experimental value _Y(x) being larger than the value of the straight line that intersects the ellipse at the largest and smallest values of x of the ellipse x-domain given by (-Bx-E)/(2C).

Check the fitteia's facebook page for more details ## Fitting a Poisson distribution

The Poission distribution has the form

P(k)=exp(-lambda)*(lambda^k)/k!

In fitteia the histogram-like fit can be obtained if the function is written as

P=(int) exp(-lambda)*pow(lambda,(int) k)/factorial((int k)) ## Concatenating columns

You can use Caculator box command select to concatenate columns from two tables in the following way:

• append your two tables, one after the other, in Data box . First table has n lines and m collumns the second table has p columns

• type "select 1:1:n, i c1 c2 ... cm and i+n c1 c2 c3 .... cp

Check the example on the side Single column input Output after:

select 1:1:4, i c1 and i+4 c1 and i+8 c1

## Working with differential equations 