=====Datasets=====

In ReMagX datasets contains the experimental data that can be viewed and fitted.

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==File format==

To load experimental results the data must be available in form of an ASCII text file with a column like organization. An example might look like:

<code>
#qz R0 R+ R-
0.00 1 1 1
0.01 0.98 0.99 0.97
0.02 0.94 0.96 ….
</code>
Note: The default separator is a tab between the columns.

The columns can represent

^ column type      ^ Description                          ^
| qz               | momentum transfer in z-direction (something like the angle of the incident ray, see next paragraph) |
| energy           | energy in eV |
| R0               | measured reflectivity (intensity of reflected light divided by the intensity of the incident ray) |
| R+               | measured reflectivity (intensity of reflected light divided by the intensity of the incident ray) |
| R-               | measured reflectivity (intensity of reflected light divided by the intensity of the incident ray) |
| Asym             | asymmetry              |
| dummy            | a column which is not used  |

Note: the file has to use the momentum transfer in z-direction, qz, as x values. The qz for a given angle Θ and energy E can be calculated as 
\\
\\
<m>q_z = 0.001013546247 Energy[eV] sin theta</m> 
\\
\\
or 
\\
\\
<m>q_z = {4 pi e} / {c h} Energy [eV] sin theta </m>
\\
\\
\\
Here, c is the speed of light, h Plancks constant and e the elementary charge quantum.

\\
\\

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Dependent on the three calculation modes (reflectivity, energy scan and asymmetry) different columns must be loaded. 

^ simulation mode            ^ columns to load            ^
| reflectivity               | qz, R0                     |
| dichroic reflectivity      | qz, R+, R-                 |
| Asymmetric reflectivity    | qz, asym                   |
|
| energy scan                | qz, energy, R0             |
| dichroic energy scan       | qz, energy, R+, R-         |
| asymmetric energy scan     | qz, energy, asym           |

It is possible to load datasets like (qz, R0, R+, R-). It will be handled properly as long as the dataset is not fitted. Since the fitting algorithm determines the dataset type dependent on this table it could be ambiguous.
So, either the normal reflectivity is fitted or the dichroic reflectivity, but not both at the same time. In this case it is recommed to separate the datasets to (qz, R0) and (qz, R+, R-)


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If you have prepared your data file go to “File” in ReMagX and choose “Load Dataset”. A file dialog appears where the position of the data file can be chosen. The next window is the data selector:
This dialog lets you choose the columns and their order in the data file. In the example to the left already two columns have been chosen, qz as first and R0 as second column.
Note: The order has to be correct. If there are columns which you don’t want to import in between place a “dummy” at their position.
You can check your selection by pressing “Preview”. If there is an error or some discrepancy between file and selection ReMagX will produce an error.

The content of the dataset file is saved in the .all file.
Imported datasets with an energy column consisting of the same values are transformed to fixed-energy measurements.
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After successfully importing the dataset into ReMagX it is necessary to activate it. Therefore choose the “Dataset” section of the “Sample” tab. In the list you will find a new entry for the imported data. It is activated by double-clicking on it.

You have to provide some additional information for the dataset so it can be handled properly by ReMagX.

^ column type      ^ Description                          ^
| Title            | Title of the measurement (default is filename) |
| Energy           | Energy in electronvolts of the used X-rays, only available in const-energy datasets |
| Energy shift     | Energy shift in electronvolts of the used X-rays, only available in non-const-energy datasets. If unsure set this value to 0.|
| Resolution       | Angular resolution of the experiment. This value is used for simulating curves. If unsure set this value to 0. |
| Scaling factor   | Scales the measurement (not the simulation). Can be used to normalize the data to 1. |
| Translation      | Adds a constant value to the measurement (not the simulation). Can be used to subtract background signals. If unsure set this value to 0. |
| qz-shift         | Adds a constant value to qz. Allows correcting angle offsets. If unsure set this value to 0. |
| Error weight     | Defines the error weighting factor of this datasets if fitted. If unsure set this to 1. |
| Polarization 1   | Defines the polarization of beam 1. At this moment valid options are s,p,l,r |
| Polarization 2   | Defines the polarization of beam 2. At this moment valid options are s,p,l,r |
| File             | Filename of the measurement data file. |
| Type             | type of data (R0, R+, R-, Asymmetry) provided by the datafile |
| Datapoints       | number of datapoints |