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{{tip|See the [httpshttp://www.nmr-relax.com/mail.gna.org/public/relax-devel/2013-06/msg00016.html mail archive] for the original post.}}
The following is a tutorial for adding new relaxation dispersion models for either CPMG-type or {{:R1rho}}-type experiments to the software relax. This includes both the models based on the analytic, closed-form expressions as well as the models involving numeric solutions of the Bloch-McConnell equations.
== Adding the model to the list ==
Firstly the model should be added to the lists of the <code>specific_analyses.relax_disp.variables </code> module. The model name is stored in a special variable which will be used throughout relax.
=== Reference commits ===
* The [[M61]] model at [http://article.gmane.org/gmane.science.nmr.relax.scm/17611 r19855]
* The [[No Rex]] model at [http://article.gmane.org/gmane.science.nmr.relax.scm/17592 r19836]
== The relax_disp.select_model user function front end ==
The next step is to add the model, its description, the equations for the analytic models, and all references to the {{uf|relax_disp.select_model }} user function front end.
== The relax_disp.select_model user function back end ==
Now the back end of the {{uf|relax_disp.select_model }} user function for the model can be added. This involved identifying the model and constructing the parameter list.
=== Reference commits ===
* The [[M61]] model at [http://article.gmane.org/gmane.science.nmr.relax.scm/17622 r19866]
* The [[No Rex]] model at [http://article.gmane.org/gmane.science.nmr.relax.scm/17592 r19836]
== Adding support for the parameters ==
This is needed to enable the model. It involves modifying many of the modules in the <code>specific_analyses.relax_disp </code> package.
=== Reference commits ===
* The [[MQ NS CPMG 2-site]] model at [http://article.gmane.org/gmane.science.nmr.relax.scm/18812 r21056]
* The [[CR72]] model at [http://article.gmane.org/gmane.science.nmr.relax.scm/17573 r19817]
== The target function ==
The target function is used in optimisation and is a class method which takes as a single argument the parameter vector. This list is changed by the minimisation algorithm during optimisation. The target function should then return a single floating point number - the chi-squared value.
Again in this example, the code for the [[M61 ]] is copied from the [[LM63 ]] model and then modified.
=== Reference commits ===
* The [[No Rex]] model at [http://article.gmane.org/gmane.science.nmr.relax.scm/17592 r19836]
* The [[CR72]] model at [http://article.gmane.org/gmane.science.nmr.relax.scm/17571 r19815]
== The relax library ==
