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Commit 9c083faa authored by Emlyn Price's avatar Emlyn Price Committed by Olivier Couet
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fitting_histograms.md formatting (#3541) 

* Fix typo with code tags in FittingHistograms.md

* Standardise presentation of TH1 and TF1 in FittingHistograms.md

There were multiple different presentations of TH1, TF1 and functions e.g.
TH1::Fit. Some TH1 and TF1 references were in bold, others were not. Likewise,
sometimes the TH1 in e.g. TH1::Fit was in bold while sometimes it was not.

This commit changes all instances of TH1, TF1 which are alone to bold and in
code tags. All instances of TH1:: or TF1:: are not in bold.
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documentation/users-guide/FittingHistograms.md
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......@@ -2,14 +2,14 @@
To fit a histogram you can use the Fit Panel on a visible histogram
via the context menu, or you can use the **`TH1`**`::Fit` method. The
via the context menu, or you can use the `TH1::Fit` method. The
Fit Panel, which is limited, is best for prototyping. The histogram
needs to be drawn in a pad before the Fit Panel is invoked. The method
`TH1::Fit` is more powerful and is used in scripts and programs.
## The Fit Method
The Fit method is implemented in ROOT for the histogram classes `TH1`,
The Fit method is implemented in ROOT for the histogram classes **`TH1`**,
the sparse histogram classes, `THnSparse`, the graph classes, `TGraph`,
`TGraph2D` and `TMultiGraph` for fitting a collection of Graphs with the same function.
......@@ -80,7 +80,7 @@ Note that in case of pre-defined functions some default initial values and limit
`polN` functions are fitted by the linear fitter.
- `*goption: `The third parameter is the graphics option that is the
same as in the **`TH1`**`::Draw` (see the chapter Draw Options).
same as in the `TH1::Draw` (see the chapter Draw Options).
- `xxmin`, `xxmax:`Thee fourth and fifth parameters specify the
range over which to apply the fit.
......@@ -91,7 +91,7 @@ is drawn in the current pad.
### The TGraph::Fit Method
The signature for fitting a TGraph is exactly the same as for the `TH1`. Only some options apply only for fitting histograms,
The signature for fitting a TGraph is exactly the same as for the **`TH1`**. Only some options apply only for fitting histograms,
these are the options "`L`", "`WL`" and "`I`".
These options apply instead only for `TGraph::Fit`, the rest of options (appart from "`L`", "`WL`" and "`I`" are the same)
......@@ -105,13 +105,13 @@ These options apply instead only for `TGraph::Fit`, the rest of options (appart
## The `TF1` function class
Here we will show how to create the `TF1` class that is used for fitting histograms and graphs.
Here we will show how to create the **`TF1`** class that is used for fitting histograms and graphs.
### Fit with a Predefined Function
To fit a histogram with a predefined function, simply pass the name of
the function in the first parameter of **`TH1`**`::Fit`. For example,
the function in the first parameter of `TH1::Fit`. For example,
this line fits histogram object `hist` with a Gaussian.
``` {.cpp}
......@@ -145,7 +145,7 @@ been adapted from the `CERNLIB` routine `G110 denlan` (see `TMath::Landau`).
You can create a **`TF1`** object and use it in the call the
**`TH1`**`::Fit`. The parameter in to the `Fit` method is the NAME of
`TH1::Fit`. The parameter in to the `Fit` method is the NAME of
the **`TF1`** object. There are three ways to create a **`TF1`**.
- Using C++ expression using x with a fixed set of operators and
......@@ -200,7 +200,7 @@ root[] f1->SetParameters(10,5);
```
This sets parameter 0 to 10 and parameter 1 to 5. We can now draw the
`TF1:`
**`TF1`**:
``` {.cpp}
root[] f1->Draw()
......@@ -270,8 +270,8 @@ Now we use the function:
```
You can create a TF1 also from a C++ function object (functor) with parameters
A TF1 can be created from any C++ class implementing this member function:
You can create a **`TF1`** also from a C++ function object (functor) with parameters
A **`TF1`** can be created from any C++ class implementing this member function:
```{.cpp}
double operator()(double *x, double *p)
......@@ -291,14 +291,14 @@ class MyFunctionObject {
};
```
and then use it to create the `TF1`:
and then use it to create the **`TF1`**:
```{.cpp}
MyFunctionObject fobj(....); // create the function object
TF1 * f = new TF1("f",fobj,xmin,xmax,npar); // create TF1 class with n-parameters and range [xmin,xmax]
```
If using C++11, one can create a `TF1` also from a C++ `lambda` function:
If using C++11, one can create a **`TF1`** also from a C++ `lambda` function:
```{.cpp}
// create TF1 class with 2 parameters and range [xmin,xmax] using a lambda
......@@ -390,7 +390,7 @@ new **`TF1`**. Each is 'derived' from the canned function `gaus`.
![Fitting a histogram with several Gaussian
functions](pictures/03000062.png)
First, four TF1 objects are created - one for each sub-range:
First, four **`TF1`** objects are created - one for each sub-range:
``` {.cpp}
g1 = new TF1("m1","gaus",85,95);
......@@ -544,7 +544,7 @@ and eventually the covariance and correlation matrix).
### Associated Function
One or more objects (typically a **`TF1`**\*) can be added to the list
One or more objects (typically a **`TF1\*`**) can be added to the list
of functions (`fFunctions`) associated to each histogram. A call to
`TH1::Fit` adds the fitted function to this list. Given a histogram
`h`, one can retrieve the associated function with:
......@@ -558,7 +558,7 @@ of functions (`fFunctions`) associated to each histogram. A call to
If the histogram (or graph) is made persistent, the list of associated
functions is also persistent. Retrieve a pointer to the function with
the **`TH1`**::GetFunction()` method. Then you can retrieve the fit
the `TH1::GetFunction()` method. Then you can retrieve the fit
parameters from the function (**`TF1`**) with calls such as:
``` {.cpp}
......@@ -830,7 +830,7 @@ fitting vectors of data points (e.g. from a `TTree`).
#### Using Binned data
Let's suppose we have an histogram, represented as a `TH1` type object (it can be one or multi-dimensional). The following shows how to create and
Let's suppose we have an histogram, represented as a **`TH1`** type object (it can be one or multi-dimensional). The following shows how to create and
fill a `ROOT:Fit::BinData` object.
``` {.cpp}
......@@ -905,7 +905,7 @@ For creating un-binned data sets, a `ROOT::Fit::UnBinData` object, one has two
inside. In this case the data cannot be selected according to a specified range. All the data points will be included in the fit.
The `ROOT::Fit::UnBinData` class supports also weighted data. In addition to the data points (coordinates), which can be of arbitrary `k` dimensions, the class can be constructed from a vector of
weights. This is an example of taking data from an histogram buffer of a `TH1` object:
weights. This is an example of taking data from an histogram buffer of a **`TH1`** object:
``` {.cpp}
double * buffer = histogram->GetBuffer();
......@@ -940,13 +940,13 @@ the independent variables **`X`** are the bin center coordinates and `Y` is the
The model function needs to be expressed as function of some unknown parameters. The fitting will find the best parameter value to describe
the observed data.
We can use the ROOT `TF1` class, the parametric function class, to describe the model function. However the `ROOT::Fit::Fitter` class, to be independent of the ROOT *`Hist`* library,
We can use the ROOT **`TF1`** class, the parametric function class, to describe the model function. However the `ROOT::Fit::Fitter` class, to be independent of the ROOT *`Hist`* library,
takes as input a more general parametric function object, the interface (abstract) class `ROOT::Math::IParametricFunctionMultiDim`, which describe a generic one or multi-dimensional function
with parameters. This interface extends the abstract class `ROOT::Math::IBaseFunctionMultiDim`, with methods to set/retrieve parameter values and to evaluate the function given the
independent vector of values **`X`** and vector of parameters `P`.
More information about the different `ROOT::Math` function interfaces is available in the Mathematical Library chapter.
An end-user can convert a `TF1` object in a `ROOT::Math::IParametricFunctionMultiDim`, using the wrapper class `ROOT::Math::WrapperMultiTF1`:
An end-user can convert a **`TF1`** object in a `ROOT::Math::IParametricFunctionMultiDim`, using the wrapper class `ROOT::Math::WrapperMultiTF1`:
``` {.cpp}
TF1 * f1 = new TF1("f1","gaus");
......@@ -955,7 +955,7 @@ An end-user can convert a `TF1` object in a `ROOT::Math::IParametricFunctionMult
fitter.SetFunction( fitFunction, false);
```
When creating the wrapper, the parameter values stored in `TF1` will be copied in the `ROOT::Math::WrappedMultiTF1` object.
When creating the wrapper, the parameter values stored in **`TF1`** will be copied in the `ROOT::Math::WrappedMultiTF1` object.
The function object representing the model function is given to the `ROOT::Fitter` class using the `Fitter::SetFunction` method.
The user has also the possibility to provide a function object, which implements the derivatives of the function with respect
......@@ -1161,7 +1161,7 @@ computes the lower/upper band values of the model function at the given data poi
covariance or correlation matrix as a `TMatrixDSym` object. In addition `TFitResult` derives from `TNamed` and can be conveniently
stored in a file.
When fitting an histogram ( a `TH1` object) or a graph (a `TGraph` object) it is possible to return a `TFitResult` via the `TFitResultPtr` object,
When fitting an histogram ( a **`TH1`** object) or a graph (a `TGraph` object) it is possible to return a `TFitResult` via the `TFitResultPtr` object,
which behaves as a smart pointer to a `TFitResult`.
`TFitResultPtr` is the return object by `TH1::Fit` or `TGraph::Fit`.
By default the TFitResultPtr contains only the status of the fit and can be obtained by an automatic conversion of the TFitResultPtr to an integer.
......
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