Go to parent GraphPad Prism statistical analyses
Prism allows to perform mathematical transformations on data. Transformation is regarded as an analysis. This is why you find the tools for transformations in the Analysis section of the top toolbar.
As an example we will transform the galileo data set. We will check the impact of the transformation on the graph of the data.
| Look at the scatter plot of the galileo data.
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We will transform the data and name the transformed data galileo square.
When you perform any analysis on your data, Prism will automatically create a new table to hold the results of the analysis. The easiest way of quickly viewing a table and all derived result tables is in the Family section of the navigator.
| Plot the square of h instead of h.
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- Click the Analyze button in the Analysis section of the top toolbar:
- This will open the Analyze data window:
- At the right you see a list of all built-in analyses in Prism. The list includes:
- Mathematical transformations: Transform, Normalize, Remove baseline, Fraction of total
- Table transformations: Prune, Transpose
- Statistical analyses: Linear regression, Column statistics, Correlation...
You have to select the analysis that you want to perform. Taking the square of a column is considered a transformation so you should select Transform.
- At the left you have to specify which data you want to analyze.
- Click OK
- This opens the Parameters window where you can set the parameters of the analysis, in our case the parameters of the transformation.
- Overview of functions in Prism that can be used for data transformation. We want to transform Y-values so we select Transform Y-values using. The drop down list shows all built-in mathematical functions. Select Y = Y squared. Click OK.
- This creates a data table containing the transformed data values called Transform of galileo.
- A results table looks different than the table that contains the original input data. It is colored green and contains a yellow window that shows details about the analysis. In our case it informs us that the table contains Y squared transformed data.
- Click the Transform of galileo graph.
- Since you have changed the Y-values, the graph of the transformed data is different from the original graph.
- To rename the transformed data and graph, right click the Tranform of galileo table and select Rename Sheet. If you change the name of the table, the graph will be renamed accordingly.
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Now we will perform an additional transformation on the galileo data. We will name the resulting table galileo sqrt.
| Plot the squareroot of h instead of h.
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Go back to the original galileo data table and proceed in exactly the same way as above.
Before the Parameters window is opened, you see a notification window to notify you that you have already performed a transformation on the data:
Choose to Analyze this table again, creating a new result sheet and click OK.
This opens the Parameters window:
This time, select Y = sqrt(Y) and click OK.
Click galileo in the Data Tables section of the navigator and expand the Family section. The data table containing the results of the transformation have been added.
Take a look at the scatter plot and rename the transformed data and graph.
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