Join
Use a Join () dataset to combine the solutions from two datasets. The Join dataset makes it possible to compare solutions from two datasets — 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 dataset has predefined methods to combine the solutions to get the difference, norm of difference, product, quotient, or sum of the two solution datasets. In addition, two predefined “operators”, data1 and data2, correspond to the solution data in the first and second Solution dataset, respectively, and make it possible to compare, for example, solutions from different but compatible models or to combine the two solution datasets 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 dataset as data1 and another dataset as data2 from the Data lists in the Data 1 and Data 2 sections, respectively.
Select which solutions to use from the Solutions lists:
Select All (the default) to use all solutions in the dataset.
Select One to use one of the available solutions in a time-dependent, parametric, or eigenvalue solution from the list of solutions that appear underneath the Solutions list.
The following dataset combinations support the option to include all solutions from both datasets:
Combination
In the Method list, select a method for combining the datasets:
Select Difference (the default) to combine the datasets using a difference: data1-data2.
Select Norm of difference to combine the datasets as abs(data1-data2), where data1 and data2 are the results of evaluating the expression in the two source datasets. For complex-valued data, this corresponds to the Euclidean norm of the difference.
Select Explicit to combine the datasets using an explicit expression with the “operators” data1 and data2 in, for example, a plot node’s Expression field. This can be useful to compare two different dependent variables in two different datasets 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 dataset and the variable v from the second dataset, times two, type 2*(data1(u)+data2(v)). The scope for data1 is the model to which the solution dataset under Data 1 belongs, and similarly for data2.
Select General to combine the datasets using a general expression in data1 and data2 that you type into the Expression field. The default, data1-data2, is identical to the Difference method. This method is useful for combining datasets with similar solution data (from a mesh convergence study, for example) using a method other than a difference, product, quotient, or sum.
Select Product to combine the datasets using a product: data1*data2.
Select Quotient to combine the datasets using a quotient: data1/data2.
Select Sum to combine the datasets using a sum: data1+data2.
If you choose Difference, for example, an operation such as sin(u) for the Join dataset 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 datasets do not match. In such cases, for example, Join datasets that contain data from a domain cannot be selected in a point plot. Also, selections are not supported when using Join datasets.