The decision tree you see rendered in your browser is created using SVG, which is a vector image format that uses mathematical expressions to create graphical images via paths. SVG images are created using text-based source code very much like HTML.

PNG is a raster image format which essentially uses grids of colored dots to create graphics, and is a binary format.

The process used in Decision Tree to translate from SVG to PNG is complicated and involves first translating the SVG code to a <canvas> element and then exporting the <canvas> to PNG. The conversion is not perfect. As an alternative to using this experimental feature, consider exporting your tree to SVG and using screen capture tools or available desktop publishing or image editing software to create raster image format versions.

Clicking the Save button will cause your decision tree to be saved as a file on the computer you are working on. The exact location is dependent on your browser settings.

Refer to Chrome and Firefox documentation to see how to set your browser preferences with regards to downloaded file location:

• Chrome "Change download locations"
• Firefox "Startup, home page and download settings"

If you select the option "Ask where to save each file before downloading", you will be prompted for an exact location where your decision tree file will be saved, and will also have an opportunity to specify the file name.
If no file name is specified, the title is used by default.

Clicking the Save as SVG and Save as PNG button will cause your decision tree to be saved as an image file on the computer you are working on. The exact location is dependent on your browser settings.

Refer to Chrome and Firefox documentation to see how to set your browser preferences with regards to downloaded file location:

• Chrome "Change download locations"
• Firefox "Startup, home page and download settings"

If you select the option "Ask where to save each file before downloading", you will be prompted for an exact location where your decision tree file will be saved, and will also have an opportunity to specify the file name.
If no file name is specified, the name defaults to "download".

Expected Values for nodes are only calculated when certain conditions are met.

• Blank and Endpoint No EV is ever calculated. Endpoint nodes have user-specified values, not "expected values".
• Chance All branches have valid probabilities assigned to them and connect to nodes that themselves have either values or expected values specified/calculated.
• Decision All branches connect to nodes that themselves have either values or expected values specified/calculated, and an objective of maximize or minimize has been set.

A decision tree is created with a certain objective in mind: either maximization or minimization of value. Without setting an objective, no decision can be rendered, and hence the purpose of constructing the decision tree cannot be fulfilled.

If for whatever reason you need the tree to be in a state where no objective is specified, perhaps because you wish to print it in a state where no pruning has been done, simply save the decision tree data by clicking Save, then reload the page in the browser, and open your saved decision tree file by clicking Open. Reloading the page resets the objective, your tree will be in a "(choose)" objective state until you set your objective again.