But
===

Extract in the form of a function the evolution of one quantity as a function of another.

If the extraction is carried out from a result data structure, or from a field of magnitude cham_gd, or from a resu_gene, the function produced corresponds to the evolution over time of a component at a node or at a Gauss point of the mesh.

From a tran_gene data structure, we can also extract the evolution of two parameters into a shock node.

From a table, you can extract the evolution of 2 parameters in the columns of the table or a function contained in a cell in the table.

From a table, you can extract the function corresponding to a given value of the parameter.

From a melasflu data structure it is possible to extract the evolution of modal parameters as a function of the fluid flow speed or the evolution of the critical speed as a function of the Connors number.

From an interspectrum data structure we can extract, the frequency evolution of the interspectrum associated with the :math:`i` -th row :math:`j` -th column of the interspectral matrix or the temporal evolution of the interspectrum with the :math:`n` -th component of the diagonal.

Produces a function or function_c data structure.

At the output of the command, the function is reordered by increasing abscissa. On the other hand, it is forbidden to have several identical abscissa (it would no longer be a function).