---
myst:
    substitutions:
        bloc:
            python: 14-15,18-19
            cpp: 4,12,14-15
---
# QQ plot

```{warning}
This function requires the "mathmore" feature to have be installed along with your {{root}} version. 
If not found, this function cannot be used and will return nothing but an equivalent to this message.
```

Once dealing with an unknown set of points, it is possible to compare it to known statistical law 
(among the following already implemented list: normal, uniform, weibull, gumbelmax, exponential, beta, 
gamma and lognormal). For instance, if one wants to compare "x2" variable from the geyser dataset to 
a normal law, one can have a look at the quantile distribution from the sample and compare it to the 
expected behaviour by following the steps below.

{{                                                                                                  
    "```{literalinclude} " + parent_dir                                                             
    + "/roottest/uranie/doc/dataserver/vizualisation/" + language + "/draw_geyser_qq." + extension 
    + "\n"
    + ":language: " + language + "\n"
    + ":lines: " + bloc[language] + "\n"                                                   
    + "```"                                                                                         
}}  

{{                                                                                                  
    "```{" "figure" "} " + parent_dir +                                                             
        "/roottest/build/uranie/doc/dataserver/vizualisation/" + language + "/geyser_10/geyser_qq.png\n"     
    ":align: center\n"                                                                              
    ":name: dataserver_geyser_qq\n"                                            
    + figure_scale + "\n"                                                                
    "\n"                                                                                            
    'Plot resulting from the "drawQQPlot" method, comparing "x2" to a normal distribution.\n' 
    "```"                                                                                           
}}

It is obvious here, that the "x2" law, clearly doesn't seem to follow a normal law (which was pretty 
obvious by looking at {numref}`dataserver_geyser_tufte` for instance). An heavy use of this method 
is provided in [](#use_cases_macro_dataserver_draw_qq_plot).