Transforming observations

The Transform tool allows you to apply a mathematical function to a variable in the dataset for all or specific observations. You can also compute something new using one or more variables.

Data can be mathematically transformed using one of the following functions:

4‑1

4‑2

4‑3

4‑4

4‑5

In these equations, Z is the output of the transformation, such as a new variable or a replaced variable, a, b, and c are user-entered constants, and X and Y are existing variables used as inputs to the transformation. X and Y can be the same as Z, but they can also be any other value in the observation.

In addition to the above equations, SoilFluxPro Software includes four other built-in transformations specific to LI-8100A systems: three soil moisture transformations and one soil temperature transformation. Each equation is named for the sensor it will be used with and assumes that the signal from the soil moisture sensor has been logged in volts.

The Decagon_EC-5 transformation uses a 3rd order polynomial, and the two DeltaT_ML3 transformations use a 6th order polynomial. The coefficients are shown in Table 4‑1.

Table 4‑1. The coefficients for soil moisture transformations.
Name a b c d e f g
Decagon EC-5 -0.612 1.16 -0.314 - - - -
DeltaT ML3 (Mineral) -0.071 0.735 0.75 -8.759 21.838 21.998 8.097
DeltaT ML3 (Organic) -0.039 0.802 0.819 -9.556 23.823 23.997 8.833

The 8150-203 Thermistor option provides the following soil temperature transformation:

4‑6

where

4‑7

and a = 1.1259 × 10−3, b = 2.3459 × 10−4, and c = 8.6329 × 10−8.

Using the transform tool

To transform a variable:

  1. Choose a function from the Function drop-down.
  2. The variables presented depend on the function you choose. We use a(X + b)/(Y + c) in this example.
  3. Select or deselect the Create New Column box as needed.
  4. This will create a new variable column labeled variable name transformed using the function, values, and units you enter. If you do not create a new column, you will need to overwrite an existing data column.
  5. Select whether to transform the variable for all or specific observations.
  6. Selected refers to observations that you have selected in the Summary view. You can tell which observations you have selected, as they will be highlighted in the Summary view. You can select observations individually by clicking on them, or you can use Ctrl + click to select multiple individual observations or Shift + click to select all observations in a range.
  7. Choose an X Variable and Y Variable.
  8. These will be the variables that are transformed. Variables in the drop-down are sorted by device.
  10. Choose an X Type and a Y Type.
  11. The options are All, Initial Value, Mean, and Range.
  13. Enter an a Value, b Value, and c Value to be used in the function.
  15. Enter a New Column Name and an Instrument Name (or you can use the default names).
  16. Enter the Units for your transformed variable.
  17. Click PREVIEW to see if the function is performing as expected.
  18. Make adjustments (if necessary), then click APPLY FUNCTION.

A new device will appear under the Measured variables based on the Instrument Name you chose.

Saving your favorite transformation

You can save your favorite transformation settings for reuse later.

Adding a favorite

Adding a favorite takes just a few steps. Once you have entered your settings as you want them, click ADD TO FAVORITES at the bottom of the page.

The Function you selected will become the name of the favorite using the X Variable and a/b Values that you entered.

Applying a favorite

To apply a favorite, click Settings. Select the favorite from the list and click APPLY FAVORITE. The settings will load in the Settings tab.

Note: To delete a favorite, select the favorite from the Favorite drop-down and click DELETE FAVORITE.