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Occasionally during the development of new features for mizer, the MizerParams object gains extra slots. MizerParams objects created in older versions of mizer are then no longer valid in the new version because of the missing slots. You need to upgrade them with

params <- upgradeParams(params)

where params should be replaced by the name of your MizerParams object. This function adds the missing slots and fills them with default values. Any object from version 0.4 onwards can be upgraded. Any old MizerSim objects should be similarly updated with upgradeSim(). This function uses newMultispeciesParams() to create a new MizerParams object using the parameters extracted from the old MizerParams object.





An old MizerParams object to be upgraded


The upgraded MizerParams object

Backwards compatibility

The internal numerics in mizer have changed over time, so there may be small discrepancies between the results obtained with the upgraded object in the new version and the original object in the old version. If it is important for you to reproduce the exact results then you should install the version of mizer with which you obtained the results. You can do this with

remotes::install_github("sizespectrum/mizer", ref = "v0.2")

where you should replace "v0.2" with the version number you require. You can see the list of available releases at

If you only have a serialised version of the old object, for example created via saveRDS(), and you get an error when trying to read it in with readRDS() then unfortunately you will need to install the old version of mizer first to read the params object into your workspace, then switch to the current version and then call upgradeParams(). You can then save the new version again with saveRDS().

See also