Heat Map

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A heatmap is a tool for displaying a map or an image. It uses data from your website to educate you about the user’s behavior graphically using different colors in the report. A heat map is a visual representation of information. Heatmaps are used to display visitor activity on your websites or web pages; they are used to indicate where users have clicked more on a page or how far visitors have scrolled down a page.

WHAT IS A HEAT MAP?

Heatmaps are colored maps that display data in a two-dimensional manner. The color maps produce color variation by using hue, saturation, or brightness to portray diverse features. This color fluctuation informs readers about the magnitude of numerical numbers. Because the human brain understands pictures better than numbers, text, or other written data, Heat Maps replaces numbers with colors. Because humans are visual learners, displaying data in whatever form makes greater sense. Heatmaps are visual representations of data that are simple to interpret. As a result, visualization methods such as Heatmaps have grown in popularity.

Heatmaps may depict patterns, variance, and even anomalies by describing the density or intensity of data. Relationships between variables are depicted using heatmaps. On both axes, these variables are displayed. We search for patterns in the cell by observing how the color changes. It accepts just numeric data and shows it on a grid, presenting different data values via altering color intensity.

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HISTORY

Heat maps evolved from 2D representations of data matrix values. Small dark grey or black squares (pixels) signified larger values, whereas lighter squares represented lower values. Toussaint Loua (1873) visualized social statistics across Paris districts using a coloring matrix. Sneath (1957) showed the findings of a cluster analysis by permuting the rows and columns of a matrix to arrange comparable values close together based on the clustering. A comparable depiction was used by Jacques Bertin to display data that corresponded to the Guttman scale. Robert Ling came up with the notion of connecting cluster trees to rows and columns of a data matrix in 1973. Ling represented multiple shades of grey with overstruck printer characters, one character-width per pixel. In 1994, Leland Wilkinson created the first computer software (SYSTAT) to generate cluster heat maps with high-resolution color images. The display displayed in the illustration by Eisen et al. is a copy of the older SYSTAT design.

Cormac Kinney, a software inventor, patented the phrase “heat map” in 1991 to represent a 2D graphic showing financial market data. The business that bought Kinney’s idea in 2003 inadvertently let the trademark lapse.

USES OF HEAT MAP

BUSINESS ANALYTICS: A heat map is used as a visual business analytics tool in business analytics. A heat map provides immediate visual clues regarding current outcomes, performance, and potential areas for development. Heatmaps may evaluate current data to identify regions of high intensity that may indicate where the majority of consumers dwell, locations at danger of market saturation, or cold sites and sites in need of a boost. Heat maps may be updated indefinitely to indicate progress and efforts. These maps may be incorporated into a company’s workflow and used in continuous analyses. To interact with team members or clients, heat maps show data in a visual and easy-to-understand format.

MOLECULAR BIOLOGY: Heat maps are used in molecular biology to examine difference and similarity patterns in DNA, RNA, and other molecules.

GEOVISUALIZATION: Geospatial heatmap charts may show how geographical areas of a map relate to one another depending on certain criteria. Heatmaps may be used in cluster analysis or hotspot analysis to identify clusters with high concentrations of activity, such as Airbnb rental pricing analysis.

EXPLORATORY DATA ANALYSIS: EDA (Exploratory Data Analysis) is a task performed by data scientists to become acquainted with the data. EDA refers to any preliminary investigations conducted to better comprehend the data. The practice of evaluating datasets prior to modelling is known as exploratory data analysis (EDA). Looking at a spreadsheet full of numbers and determining important qualities in a dataset is a time-consuming activity. As a result, EDA is used to highlight their essential aspects, frequently using visual approaches like as Heatmaps. Heatmaps are a powerful tool for visualizing correlations between variables in high-dimensional space. It is possible to achieve this by utilizing feature variables as row and column headings, and the variable vs. itself on the diagonal.

WEBSITE:  Heatmaps are used on websites to illustrate visitor activity data. This visualization assists company owners and marketers in determining the best and worst performing portions of a website. These insights aid in optimization.

MARKETING AND SALES: The capacity of the heatmap to detect hot and cold locations is utilized to boost marketing response rates through targeted marketing. Heatmaps enable the discovery of locations that react to campaigns, underserved markets, customer residence, and high sale trends, which aids in the optimization of product lineups, capitalization on sales, the creation of targeted customer segments, and the assessment of regional demographics.

SOFTWARE IMPLEMENTATION OF HEAT MAP

  • Heat map visualization in MATLAB comes with a plethora of setup choices. To create bespoke heatmaps, Seaborn, a Python library built on top of the matplotlib framework, is utilized. Seaborn heatmap visualizes the correlation matrix, which aids in EDA, feature selection, and problem solving.
  • Heatmaps may be traced in the R software environment using the heatmaply R package.
  • Google Fusion Tables allows you to generate a heat map from a Google Sheets spreadsheet with a maximum of 1000 geographic data points.
  • Openlayers3 can create a heat map layer based on a certain attribute of all geographic features in a vector layer.
  • D3.js is a java data visualization framework that can generate dynamic heat map charts.
  • Gnuplot is a command-line graphing software that can trace both 2D and 3D heat maps.
  • Fusion Charts: Fusion Charts is a charting and visualization application written in JavaScript. It can generate 90 various sorts of charts. Users may create rapid visualizations by choosing from a variety of templates rather than beginning from scratch and just putting in their data sources as required.
  • Highcharts: Because Highcharts is cross-browser compatible, anybody may see and execute its interactive visualizations. It enables a quick and versatile solution with little data visualization expertise.
  • Datawrapper: Datawrapper features an easy-to-use interface for uploading CSV data and creating clear charts and maps that can be incorporated in reports. It is a popular option among media companies, who use it regularly to make charts and report information.

COLOR SCHEMES

Many various color schemes may be used to depict the heat map, each with its own set of perceptual advantages and disadvantages. Color palette selections are more than simply aesthetics since the colors in the Heat Map reflect data patterns. Pattern discovery can be aided by good color schemes, but it can also be hampered by poor color selections.

The following are general guidelines for utilizing colors in Heatmaps:

To differentiate categories, vary the hue: Change the color of the pieces to indicate different story types. Most people can distinguish between a limited number of hues. Colors are the greatest way to indicate categories.

Vary the luminance to depict numbers: Varying the luminance allows you to discern structure in numerical data. Luminance variation improves the visibility of discrete or continuous patterns in a bivariate distribution. The brightness color scheme additionally highlights the presence of two strong peaks.

BEST PRACTICES TO USE A HEAT MAP

Color palette: Because color is an important component of a heatmap, the color palette should match the data type. Between value and color, a sequential color bar is employed, with lighter hues corresponding to lower quantities and darker shades corresponding to bigger values, or vice versa. When values have a zero point, a diverging color palette is employed.

Legend: Because colors have no natural link with numeric values, a legend is required for viewers to comprehend the heatmap’s contents. A key is helpful for displaying the mapping of colors to numerical values.

Annotate: Because there is a lack of precision in mapping color to value, it is beneficial to add cell value annotations to the heatmap.

Sort: It is advisable to plot the numeric variables on the heatmap in sorted order; this helps readers understand the data patterns. Because categories do not have a natural ordering, a common practice is to sort them by their average cell value. The clustered heatmap groups category values based on their closeness.

Tick markings: Tick marks normally correlate to the number of bins, which varies depending on the type of the data. If there are few bins on a numeric axis variable, it is permissible to maintain tick marks on each bin. When there are numerous bins, however, putting check marks between groups of bins is preferable to minimize congestion. It is suggested to preserve tick marks on each bin for a categorical axis variable.

COLOR PALETTES

Seaborn Color Palletes: The Color Palletes are a complete set of digital colors used for seaborn visualizations.

The color palette() seaborn function offers an interface for creating color palettes in seaborn. Name of a seaborn palette (deep, muted, brilliant, pastel, dark, colorblind), Name of a matplotlib colormap, ‘ch:cubehelix arguments>’, ‘husl’ or ‘hsl’, ‘light:color>’, ‘dark:color>’, ‘blend:color>,color>’, or A color sequence in any format that matplotlib allows. The set palette() method sets the default palette, which internally calls color palette() and accepts the same inputs.

QUALITATIVE PALETTE: Colors in a qualitative palette typically include differences in their hue component; hence, qualitative palettes are appropriate for representing categorical data. The default color palette of the seaborn is a ‘qualitative palette.’ Deep, muted, pastel, brilliant, dark, and colorblind are the six matplotlib palette options available in Seaborn.

The simplest way to identify unique hues is to draw equally spaced colors in a circular color space for an arbitrary number of categories; the HSL and HUSL color spaces employ this method.

SEQUENTIAL PALETTE: Because luminance is the dominant dimension of variation in a sequential palette, it is suitable for displaying numerical data. When data ranges from relatively low or boring values to relatively high or fascinating information, sequential color mapping is ideal. For categorical data, Seaborn employs the discrete version of the sequential palette, whereas for numeric data, he employs the continuous version. Discrete sequential colormaps can also be used to visualize categorical data. Sequential colormaps are ideal for data that rises gradually and linearly. Every sequential colormap has a reversed variant, which is denoted by the suffix “_r.”

  • Palettes that are perceptually uniform: Seaborn comes with four successive colormaps that are perceptually uniform: “rocket,” “mako,” “flare,” and “crest.” The first two have a wide brightness range and are ideal for application such as heat map.
  • Successive cubehelix palettes: The cubehelix system provides an RGB-based tradeoff, producing sequential palettes with a linear rise or drop in brightness and some continuous fluctuation in color. The resultant colormaps are not exactly perceptually homogeneous, but the design process is parameterizable. The palette’s appearance is controlled by cubehelix palette().
  • Custom sequential palettes: A single color value is supplied to either light palette() or dark palette(), which generates a palette that begins with light or dark desaturated values and progresses to that color.
  • Sequential Color Brewer palettes: The Color Brewer collection includes palettes with a single primary hue.

DIVERGING PALETTE: Diverging palettes can be used to depict numerical data with a category border. The diverging color palette generates a colormap by combining the divergence of two colors. These are used for data that has both low and high values that are outstanding and span a middle value that should be de-emphasized. Diverging palettes have two dominating colormap colors, one at each pole. It is also critical that the beginning values have comparable brightness and saturation.

Perceptually uniform diverging palettes: “vlag” and “icefire” are two perceptually uniform diverging palettes in Seaborn.

Diverging palettes made to order: Diverging palette() is a function that generates a custom colormap for diverging data. It creates colormaps with a single color on each side. It requires two colors as parameters, both of which are convergent to another color in the center. Correlations range from -1 to 1, so they have two directions, and in this case, a diverging palette works better than a sequential one.

INPUTS OF HEAT MAP

Wide-format: Wide-format, commonly known as Untidy Format, is a matrix in which each row represents a person, and each column represents an observation. In this scenario, the color of a heatmap cell correlates to the observation value.

Correlation matrix: A correlation matrix, commonly known as a square format, is generated by applying the corr() function on a dataset and is shown on a heatmap. Such Heatmaps aid in determining which factors are connected to one another.

Long-format: Long-format, often known as tidy format, is when each line reflects an observation. Individual, variable name, and value are the three columns (x, y, and z). This type of data may be used to generate a heatmap, as seen below:

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DATA ANALYSIS OF HEAT MAP

  • The largest positive link with alcohol is found in wine quality, followed by sulphates and citric acid.
  • Volatile acidity has the most negative link with wine quality, followed by density and chlorides.
  • If we need to reduce the dimensionality of a model, we can remove characteristics that correlate closer to zero, such as residual sugar, sulfur dioxide, pH, and constant acidity.
  • For feature selection, one of the characteristics having a significant association with other components might also be excluded. One of the ‘free sulfur dioxide’ or ‘total sulfur dioxide’ characteristics may be removed (depending upon further analysis)

TYPES OF HEATMAP

GRID HEATMAP

A density-based function is used to lay out the magnitudes of values shown through colors into a matrix of rows and columns. Grid Heatmaps are classified as follows.

Clustered Heatmap: The purpose of Clustered Heatmap is to create relationships between data points and their characteristics. Clustering is used as part of the process of grouping comparable characteristics in this sort of heatmap. Clustered Heatmaps are commonly used in biological sciences to investigate gene similarities between people

Correlogram: A correlogram substitutes each of the variables on the two axes with numerical variables in the dataset. Each square represents the link between two intersecting variables, which aids in the development of descriptive or predictive statistical models.

SPATIAL HEATMAP

Each square in a Heatmap is assigned a color representation based on the value of the neighboring cells. The magnitude of the value in that space determines the placement of color. These Heatmaps are data-driven “paint by numbers” canvas overlays layered on top of images. Cells with greater values than other cells are colored hot, whereas cells with lower values are colored cool.

CHOROPLETH V/S HEATMAP

Heat maps and choropleth maps are frequently mistaken. A choropleth map shows the percentage of a variable of interest by using varying shading patterns within geographic boundaries. A heat map, on the other hand, does not correlate to geographic limits. Choropleth maps depict the variability of a variable over time or over a geographic area. Instead of the a priori geographic areas of choropleth maps, a heat map employs regions generated according to the variable’s pattern. The Choropleth is divided into well-known geographical entities including nations, states, provinces, and counties.

ADVANCED HEATMAP

CORRPLOT

Regular Heatmaps make it simple to discern between negative correlation, positive correlation, and no correlation features, but examining the values of positive correlation among positively correlated variables still necessitates going over the grid several times. To make our maps more legible, we add size as a parameter to our heatmap in addition to color. Each colored square’s size is proportional to the magnitude of the association. It also provides insight about the marginal distributions without requiring the use of a color graphic.

c = corrplot.Corrplot(data.corr())

c.plot(cmap=’coolwarm’, method=’square’, shrink=.9 ,rotation=45)

CLUSTER HEATMAP

Clustering is used as part of the process of grouping comparable characteristics in this sort of heatmap. Inherently Clustering methods are used to group together related rows on a map. The order of the columns is also chosen.

sns.clustermap(data.corr(), cmap=”coolwarm”)

ADVANTAGES OF HEAT MAP

  • Heatmaps assist businesses in making educated decisions that boost their bottom line: Heatmaps facilitate business decisions by assisting managers in making better web design choices that increase engagement and conversions that lead to sales. Finally, heatmaps are all about increasing revenue. Customers value their ROI, as seen by the widespread usage of heatmap online diagnostic tools.
  • Effective graphics demonstrate clear conclusions: This Wall Street Journal piece from 2015 has heatmaps that are both practical and appealing. Each graph depicts the number of cases of an infectious illness as well as the date on which a vaccine was released. These charts are also interactive in the sense that you can hover over them to get more information.
  • Gives direct overview of web performance: A click heatmap illustrates the users’ clicking tendencies. The average visibility of pages is revealed through heatmaps. Attention reveals which portions of your website are the most appealing to consumers. Mouse motions are tracked. Finally, geo heatmaps show which areas or nations have high conversion rates and which do not.
  • Understand your vision better and provide them better experience: Users are vital because they are a part of the dialogue, whether the objective is to sell a service, a product, or an idea. That implies you must be interested in knowing how people react to your message and whether you need to improve it in a new way. This entails determining what irritates or distracts your consumers, which is why friction scores on heatmaps can be so useful. A solution like this may automatically track data to show you where and when the user is frustrated. Heatmap filters may demonstrate how diverse your audience responds to the same message. Listening to a specific audience allows you to provide a better experience for them.

DISADVANTGES OF HEAT MAP

  • Color is difficult to transfer into a continuous scale.

There are various exceptions to this rule, so it is not always a deal breaker, but in the case of heat maps, the problem is especially tough since our perception of a color changes based on the colors around it. As a result, even with tiny data sets, heat maps are unsuitable for viewing individual findings. This results in:

  • Answering particular queries with a table look-up approach is often not practicable since it is impossible to derive the numerical value corresponding to a given hue with sufficient accuracy.
  • Often, data is not grouped in such a way that patterns may be identified.
  • Without such clustering, inferring anything about general overarching patterns is frequently difficult or impossible.
  • Heat maps are frequently employed to convey a “wow factor” or just to look great, particularly when utilizing a multicolor gradient, however there are typically better ways to present the data.
  • The ideal choice is to plot continuous data on a similar scale. A line plot is the natural choice when there is a time component.

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Hindol Basu 
GM, Voxco Intelligence

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