Join

) data set to combine the solutions from two data sets. The Join data set makes it possible to compare solutions from two data sets — for example, to evaluate and visualize the difference between two solutions to the same problem using two different meshes in a mesh convergence study or to create the sum over a parametric sweep that contains a few solutions. The Join data set has predefined methods to combine the solutions to get the difference, norm of difference, product, quotient, or sum of the two solution data sets. In addition, two predefined “operators”, data1 and data2, correspond to the solution data in the first and second Solution data set, respectively, and make it possible to compare, for example, solutions from different but compatible models or to combine the two solution data sets using a method other than the ones that you can select directly.


	You can also use the withsol operator in a plot expression, for example, to combine solutions from different solver sequences. See withsol for more information.

Data 1 and Data 2

Select a solution data set as data1 and another solution data set as data2 from the lists in the and sections, respectively.

Select which solutions to use from the lists:

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Select (the default) to use all solutions in the data set.

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Select to use one of the available solutions in a time-dependent, parametric, or eigenvalue solution from the list of solutions that appear underneath the list.

The following data set combinations support the option to include all solutions from both data sets:

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Both data sets point to the same solution.

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Both data sets point to two different stationary solutions.

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Both data sets point to two different time-dependent solutions.

Combination

In the list, select a method for combining the solution data sets:

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Select (the default) to combine the data sets using a difference: data1-data2.

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Select to combine the data sets as abs(data1-data2), where data1 and data2 are the results of evaluating the expression in the two source data sets. For complex-valued data, this corresponds to the Euclidean norm of the difference.

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Select to combine the data sets using an explicit expression with the “operators” data1 and data2 in, for example, a plot node’s field. This can be useful to compare two different dependent variables in two different data sets such as two solutions from two different models using the same geometry. For example, to plot the sum of the variable u from the first data set and the variable v from the second data set, times two, type 2*(data1(u)+data2(v)). The scope for data1 is the model to which the solution data set under belongs, and similarly for data2.

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Select to combine the data sets using a general expression in data1 and data2 that you type into the field. The default, data1-data2, is identical to the method. This method is useful for combining data sets with similar solution data (from a mesh convergence study, for example) using a method other than a difference, product, quotient, or sum.

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Select to combine the data sets using a product: data1*data2.

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Select to combine the data sets using a quotient: data1/data2.

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Select to combine the data sets using a sum: data1+data2.


	If you choose Difference, for example, an operation such as sin(u) for the Join data set is equivalent to sin(data1(u))-sin(data2(u)). If you want to evaluate or plot sin(u) as the operator applied to the difference itself, for example, choose Explicit and use sin(data1(u)-data2(u)) as the expression to evaluate or plot.


	It can happen that the geometries in the two data sets do not match. In such cases, for example, Join data sets that contain data from a domain cannot be selected in a point plot. Also, selections are not supported when using Join data sets.