Description Usage Arguments Details Value Author(s) References See Also Examples

View source: R/profitCubaBrokenExp.R

Useful functions related to the broken-exponential profile. `profitCubaSersic`

computes the exact 2D pixel integrals for a given broken-exponential model image. This is very slow compared to `profitMakeModel`

, but it is useful for checking model creation tuning (i.e. the degree to which speed can be increased without overly harming accuracy). Tests with this function were used to tune `profitMakeModel`

. `profitRadialSersic`

computes the 1D radial flux intensity of the broken-exponential profile along the major axis of the profile.

1 2 3 4 5 |

`xcen` |
Scalar; x centre of the 2D broken-exponential profile (can be fractional pixel positions). |

`ycen` |
Scalar; y centre of the 2D broken-exponential profile (can be fractional pixel positions). |

`r` |
Vector; the radius along the major axis at which to evaluate the flux intensity. |

`mag` |
Scalar; total magnitude of the 2D broken-exponential profile. Converted to flux using flux=10^(-0.4*(mag-magzero)). |

`h1` |
Scalar; scale length of the inner broken-exponential profile. |

`h2` |
Scalar; scale length of the outer broken-exponential profile. |

`rb` |
Scalar; break (or truncation) radius of the broken-exponential profile. |

`a` |
Scalar; strength of transition from inner core to outer broken-exponential. Larger +ve means sharper. |

`ang` |
Scalar; the orientation of the major axis of the Sersic profile in degrees. When plotted as an R image the angle (theta) has the convention that 0= | (vertical), 45= \, 90= - (horizontal), 135= /, 180= | (vertical). Values outside the range 0 <= ang <= 180 are allowed, but these get recomputed as ang = ang. |

`axrat` |
Scalar; axial ratio of the Sersic profile defined as minor-axis/major-axis, i.e. 1 is a circle and 0 is a line. |

`box` |
Scalar; the boxiness of the Sersic profile that traces contours of iso-flux, defined such that r[mod]=(x^(2+box)+y^(2+box))^(1/(2+box)). When box=0 the iso-flux contours will be normal ellipses, but modifications between -1<box<1 will produce visually boxy distortions. Negative values have a pin-cushion effect, whereas positive values have a barrel effect (the major and minor axes staying fixed in all cases). |

`dim` |
Scalar; the dimensions of the image to be generated. Typically this should be c(Nx,Ny). If length 1 then the value will be replicated for both dimensions. |

`rel.tol` |
Scalar; the requested relative accuracy. Default, 0.001. |

`abs.tol` |
Scalar; the requested absolute accuracy. The algorithm stops when either the relative or the absolute accuracies are met. Default, near 1e-10. |

`plot` |
Logical; should a |

`...` |
Further arguments to be passed to |

This function uses the Cuba package to make an accurate (but expensive) cubature integral. This function was written to test the accuracy of ProFit Core-Sersic models generated by `profitMakeModel`

.

By ProFit convention the bottom-left part of the bottom-left pixel when plotting the image matrix is c(0,0) and the top-right part of the bottom-left pixel is c(1,1), i.e. the mid-point of pixels are half integer values in x and y.

To confuse things a bit, when R plots an image of a matrix it is transposed and re-ordered vertically to how it appears if you print the matrix directly to screen, i.e. compare print(matrix(1:4,2,2)) and image(matrix(1:4,2,2)). The lowest value (1) is top-left when printed but bottom-left when displayed using image (the red pixel). Both are "correct": the issue is whether you consider the first element of a matrix to be the Cartesian x position (movement in x) or a row element (movement in y). Matrices in maths are always written top-left first where the first argument refers to row number, but images by convention are accessed in a Cartesian sense. Hence [3,4] in a maths matrix means 3 down and 4 right from the top-left, but 3 right and 4 up from the bottom-left in an image.

`profitCubaBrokenExp`

:
Matrix; contains the flux values of the specified model image. Dimensions dim.

`profitRadialBrokenExp`

:
Vector; same length as input r, specifying the flux intensity of the profile along the major axis.

Aaron Robotham

Erwin, P., Pohlen, M., & Beckman, J. E. 2008, AJ, 135, 20

`profitMakeModel`

, `profitSersic`

, `profitMoffat`

, `profitFerrer`

, `profitKing`

1 2 3 4 | ```
## Not run:
magimage(profitCubaBrokenExp(axrat=0.7, ang=30, h1=6, h2=3, rb=4, a=1))
## End(Not run)
``` |

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