# ARTS built-in documentation server

## Workspace Method iyLoopFrequencies

### Description

Radiative transfer calculations one frequency at the time. The method loops the frequencies in f_grid and calls iy_loop_freqs_agenda for each individual value. This method is placed in iy_main_agenda, and the actual radiative transfer method is put in iy_loop_freqs_agenda. A common justification for using the method should be to consider dispersion. By using this method it is ensured that the propagation path for each individual frequency is calculated.

**Authors: **Patrick Eriksson

### Synopsis

iyLoopFrequencies( | iy, iy_aux, ppath, diy_dx, iy_aux_vars, iy_agenda_call1, iy_transmittance, rte_pos, rte_los, rte_pos2, stokes_dim, f_grid, iy_loop_freqs_agenda ) |

### Variables

OUT | iy | (Matrix) | Monochromatic pencil beam radiance spectrum. |

OUT | iy_aux | (ArrayOfMatrix) | Data auxiliary to iy. |

OUT | ppath | (Ppath) | The propagation path for one line-of-sight. |

OUT | diy_dx | (ArrayOfTensor3) | Derivative of iy with respect to retrieval quantities. |

IN | iy_aux_vars | (ArrayOfString) | Selection of quantities for iy_aux and when applicable also y_aux. |

IN | iy_agenda_call1 | (Index) | Flag to handle recursive calls of iy_main_agenda The agenda iy_main_agenda can be used recursively and this flag is used to tell the methods inside the agenda which is the primary call. |

IN | iy_transmittance | (Tensor3) | Transmittance to be included in iy. |

IN | rte_pos | (Vector) | A geographical position for starting radiative transfer calculations. |

IN | rte_los | (Vector) | A line-of-sight for (complete) radiative transfer calculations. |

IN | rte_pos2 | (Vector) | A second geographical position to define the geometry for radiative transfer calculations. |

IN | stokes_dim | (Index) | The dimensionality of the Stokes vector (1-4). |

IN | f_grid | (Vector) | The frequency grid for monochromatic pencil beam calculations. |

IN | iy_loop_freqs_agenda | (Agenda) | Agenda dedicated to iyLoopFrequencies. |