GSoC: Adding Histogram Chart Update Week 10 and Week 11(this)

[Devansh Varshney <varshney.devansh614@xxxxxxxxx>]

Hi,

So last week my mentor Tomaž set the direction of the descent towards a working Histogram which is now successfully merged with master https://gerrit.libreoffice.org/c/core/+/167068

As I kept looking to modify the View for the Histogram which was quite late to do so and hence he set up two file HistogramDataSequence and HistogramDataInterpreter as the name suggests handling sequence of data and interpreting it in separate logic.

and as I used square root to calculate the number of bins which was easier to test with(for me) which was later pointed out that we should be using what MS-Office is using and my mentor pointed me https://support.microsoft.com/en-us/office/create-a-histogram-85680173-064b-4024-b39d-80f17ff2f4e8#ID0EBBDBBJBJ-panel Scott’s normal reference (By Default) and as off now I do have created a separate commit for this which I corrected/aligned over the last week- https://gerrit.libreoffice.org/c/core/+/170526

We are still not having the exact same values as in the MS-Office ones, which still needs some calculation(rounding/approximation) corrections.

MS-Office vs. Our Implementation -

Google Sheet vs. Our Implementation -

There is a blog about Hisotgram and its working by MSO  http://web.archive.org/web/20160117042913/https://blogs.office.com/2015/08/18/visualize-statistics-with-histogram-pareto-and-box-and-whisker-charts/

Second, I also made a mistake in how we perceive/begin the bin range?

   I believed that creating Bin Ranges was similar to filling a glass with water, wherein we begin by including the beginning(base) until below the top(to avoid overflow), akin to filling a glass of water.

                        i.e. [Glass of Water)

But, this is not how MS-Office is doing rather it was (Glass of Water] & can be seen in the above imageries. Hence, made change to the code -

// Set up bin ranges

maBinRanges.reserve(mnBins);

double fBinStart = fMinValue;

for (sal_Int32 i = 0; i < mnBins; ++i)

{

double fBinEnd = fBinStart + mfBinWidth;

// Correct rounding to avoid discrepancies

fBinStart = std::round(fBinStart * 100.0) / 100.0;

fBinEnd = std::round(fBinEnd * 100.0) / 100.0;

if (i == 0)

{

// First bin includes the minimum value, so use closed interval [fMinValue, fBinEnd]

maBinRanges.emplace_back(fMinValue, fBinEnd);

}

else

{

// Subsequent bins use half-open interval (fBinStart, fBinEnd]

maBinRanges.emplace_back(fBinStart, fBinEnd);

}

fBinStart = fBinEnd;

}

// Create labels and values for HistogramDataSequence

std::vector<OUString> labels;

std::vector<double> values;

for (size_t i = 0; i < binRanges.size(); ++i)

{

OUString label;

if (i == 0)

{

label = u"[" + OUString::number(binRanges[i].first) + u"-"

+ OUString::number(binRanges[i].second) + u"]";

}

else

{

label = u"(" + OUString::number(binRanges[i].first) + u"-"

+ OUString::number(binRanges[i].second) + u"]";

}

labels.push_back(label);

values.push_back(static_cast<double>(binFrequencies[i]));

}

i.e. A data point is included in a particular bin if the number is greater than the lowest bound and equal to or less than the greatest bound for the data bin.

Now, these above two changes are still needs to be added /merge to replace the square root method.

There is one more thing which can be seen easily is the color of the bins in our implementation and which is also being pointed out by Stéphane in the testing https://bugs.documentfoundation.org/show_bug.cgi?id=162135

    Me and my mentor, we both did have a conversation on this that this is probably due to as we are creating a new DataSeries instead of reusing the existing one. For example, since we are inheriting BarChart view to reuse the code for creating and rendering the bars.

void HistogramChart::createShapes()

{

if (m_aZSlots.empty()) //No data series Available

return;

OSL_ENSURE(

m_xLogicTarget.is() && m_xFinalTarget.is(),

"HistogramChart is not properly initialized"); // Ensuring chart is properly initialized

if (!(m_xLogicTarget.is() && m_xFinalTarget.is()))

return;

adaptGapWidthForHistogram();

BarChart::createShapes();

}

Have to discuss this and also looking for more feedback as New histogram chart implemented in 25.2 by 07ae0e5ada7cb595eb4815413a5bdd442c32a6ab for bug 82716

For this week which is 11 My goal is to get the OOXML and ODF support added for the histogram http://officeopenxml.com/

The way I have understood OOXMl and ODF as sort of Container File (which could be thought of zip file) since we are using XML files for reading parsing and loading the struture how it should look on the UI or presented to the user.

The every first time I came across this kind of usage of XML when I was making a small software using Qt ( https://github.com/varshneydevansh/EFM-DC_V2 ) where for the UI I came across the usage of XML file.

So, for this if I am correct is had to make the Histogram correctly able to read and write its content in XML files so that we can use it efficiently.

OOXML - Microsoft Office applications like Excel (.xlsx), Word (.docx), and PowerPoint (.pptx).         oox/source/ directory

ODF - Used by LibreOffice applications like Calc (.ods), Writer (.odt), and Impress (.odp).                 xmloff/source/chart/ directory

How Do Import and Export Work?

Importing (Reading)

When we import an OOXML or ODF file:

1. The software unzips the archive.
2. It reads the XML files inside.
3. It parses the XML data to understand the content and structure (e.g., charts, tables, text).
4. It loads this data into the application (like LibreOffice Calc or Excel) for us to work with.

Exporting (Saving)

When we export to an OOXML or ODF file:

1. The software gathers the data from the application.
2. It formats this data into XML according to the OOXML or ODF standards.
3. It creates new XML files or updates existing ones inside the archive.
4. It zips the files into a single archive (e.g., .xlsx or .ods).

Not just this also have to look at the testing results a.k.a the bugs which are now being reported.

and soon work for the Pareto Chart :)

From: Devansh Varshney <varshney.devansh614@xxxxxxxxx>
Date: Thu, 11 Jul 2024 at 00:30
Subject: GSoC: Adding Histogram Chart Native Support (Week 8, prev) and (Week 9, this)
To: <libreoffice@xxxxxxxxxxxxxxxxxxxxx>

Hi,

So, the previous week I did not send the weekly update as I was hopeful that I am close to get this done

and kept pushing to not only get the X and Y axis with proper Bin Range and Frequency but also the bar

for the Histogram plot. But, I also find the scaling issue which I encountered by the end of the week.

Here, I am using the analogy of Gradient Descent part of Mathematical Optimization to explain the situation.

In the beginning of the May, we started off from the top region (Red) with the highest cost of instability for

the addition of the changes. By the end of May we were able to have the Histogram specific code but mimicking

Bar/Column Chart and in the beginning of the June we were able to have the bars attached to each other, 

i.e., with ZERO gap between each other.

 

After having this as a success, we went on our next step, which was to get the X and Y axis as Bin Ranges and Frequency.

Which could be thought of as somewhere around the location of Saddle point. From here instead of going towards the

global minima I went towards the local minima, which is got stuck with the axes' modification.

Though in local minima which took me almost 4 weeks I kept revolving into it and the result was by last week -

            

```bash

i/p- 12,10,15,16,14

o/p -

Entering createShapes()
xSeriesTarget is valid: true
xTextTarget is valid: true
m_nBins: 2, m_fBinWidth: 3
minValue: 10, maxValue: 16
m_binRanges: {10, 13} {13, 16}
m_binFrequencies: 3 2
Bin ranges size: 2
Bin frequencies size: 2
Entering doXSlot() for bin index: 0
Bar dimensions - X: 0.25, Width: 0.5, Height: 1
Exiting doXSlot()
Entering doXSlot() for bin index: 1
Bar dimensions - X: 0.75, Width: 0.5, Height: 0.666667
Exiting doXSlot()
Exiting createShapes(

```

I was able to have the bars which were 2 as I am using the sqrt method to calculate the number of bins as of now.

After having been stuck in the local minima for so long, my mentor Tomaž came forward and change the direction of the

descent from the local minima towards the global minima by creating the chart2/source/model/template/HistogramDataInterpreter.cxx

and chart2/source/tools/HistogramDataSequence.cxx where we are currently having the X and Y axis values and dummy values

Hard-coded -

         

In the above images which were being generated via the help of HistogramDataInterpreter the first image is taking the BarChart

as the base hence bars with gaps -

chart2/source/view/charttypes/VSeriesPlotter.cxx -

```cpp

else if( aChartType.equalsIgnoreAsciiCase( CHART2_SERVICE_NAME_CHARTTYPE_HISTOGRAM ) )