13. A system comprising: one or more computers configured to perform a method comprising: presenting a graphical user interface of a web application on a client device, wherein the graphical user interface presents multiple cells in a matrix of cells, wherein each cell is an interactive element; executing a first script found in a first cell of the multiple cells, the first script invoking (i) a first model of a plurality of predictive models using data of a first plurality of the cells to train the first model and (ii) a second model of the plurality of predictive models using the data of the first plurality of the cells to train the second model; and executing a second script found in a second cell of the multiple cells, the second script invoking (i) the trained first model with data from a second plurality of cells as input and using output from the trained first model to determine a value of a third cell in the matrix of cells, and (ii) the trained second model with data from the second plurality of cells as input and using output from the trained second model to determine a value of a fourth cell in the matrix of cells.
13. A system comprising: one or more computers configured to perform a method comprising: presenting a graphical user interface of a web application on a client device, wherein the graphical user interface presents multiple cells in a matrix of cells, wherein each cell is an interactive element; executing a first script found in a first cell of the multiple cells, the first script invoking (i) a first model of a plurality of predictive models using data of a first plurality of the cells to train the first model and (ii) a second model of the plurality of predictive models using the data of the first plurality of the cells to train the second model; and executing a second script found in a second cell of the multiple cells, the second script invoking (i) the trained first model with data from a second plurality of cells as input and using output from the trained first model to determine a value of a third cell in the matrix of cells, and (ii) the trained second model with data from the second plurality of cells as input and using output from the trained second model to determine a value of a fourth cell in the matrix of cells. 18. The system of claim 13 , wherein the output from the trained first model is a prediction by the trained first model that is based on the data from the second plurality of cells and the output from the trained second model is a prediction by the trained second model that is based on the data from the second plurality of cells.