xlsgen > overview > Forecast chart

Chart forecast allows to predict future values of a measure.

Contrary to the existing trendline foreward capabilities which provide a simple mechanism for projecting a regression curve with the obvious limit that it is projecting itself, forecast actually infers future values without a regression curve as a model.

In the picture above, the continuous line is the data and the dashed line is the forecast values. Dash denotes the non-actual nature of what is depicted, compared to the continuous line. Continuous and forecast values are tied together where the data ends, which also is where forecast begins.

xlsgen computes everything so there is no need for prior knowledge for mathematical/statistical models. Creating a chart of type forecast and attaching one or more data series to it is all what is needed.

xlsgen::IXlsChartPtr chart = wksht->NewChart(xlsgen::charttype_forecast, 4, 3, 18, 8);
xlsgen::IXlsChartDynamicDataSourceSeriesPtr serie001 = chart->DynamicDataSource->AddSerie();
serie001->DataLabelsFormula   = L"=C3:C21";
serie001->SeriesValuesFormula = L"=D3:D21";