# Correlation - Distances

Computes a *distance matrix* comparing variables or cases. If a case contains missing values, it is omitted from the analysis. Weights are not applicable when comparing cases. See What is a Distance Matrix? for more information about distance matrices.

## How to Create a Distance Matrix

- Add the object:
- In
*Displayr:***Insert > More > Correlation > Distances** - In
*Q:***Create > Correlation > Distances**

- In
- Under
**Inputs > Compare**select if you want to compare*variables*or*cases.*Please note you can only compare 100 cases or fewer.- If cases are compared, select the
*Case label*to use. This is the label to use to refer to each case. If nothing is selected, the case index is used.

- If cases are compared, select the
- Under
**Inputs > Variables**select the variables to compare. At least two variables must be selected.

## Example

Distance matrices are displayed as triangular heatmaps. The example below is a *dissimilarity matrix* using data from a cola consumption survey.

## Options

The options in the Object Inspector are organized into two tabs: **Inputs** and **Properties**.

### Inputs

**Compare** Whether variables or cases are to be compared.

**Case labels** If cases are compared, these are the labels to use to refer to each case. Otherwise, the case index is used.

**Variables** The variables that will be included in this analysis.

**Variable names** Whether to display Variable Names in the output instead of Variable Labels.

**Categorical as binary** Represents unordered categorical variables as binary variables. Otherwise, they are represented as sequential integers (i.e., 1 for the first category, 2 for the second, etc.). *Numeric - Multi* variables are treated according to their numeric values and not converted to binary.

**Measure** Whether to measure similarities or dissimilarities.

**Similarity measure** The type of similarity measure to use:

**Correlation**Pearson correlation.**Cosine**The cosine of the angle between a pair of vectors which represent a pair of variables or cases.

**Distance measure** The type of distance/dissimilarity measure to use. The options are (refer to `dist` for more information):

**Euclidean****Squared Euclidean**The square of the Euclidean distance**Maximum****Manhattan****Minkowski**

**Minkowski power (p)** The power parameter for the Minkowski distance measure.

**Data standardization** The standardization method. Choices include:

**None**No standardization is performed.**z-scores**Values are transformed to have mean zero and a standard deviation of one.**Range [-1,1]**Values are divided by their range.**Range [0,1]**Values are subtracted by their minimum value and divided by their range.**Mean of 1**Values are divided by their mean. If the mean is zero, the values will be unchanged.**Standard deviation of 1**Values are divided by their standard deviation.

For methods that require variation in the values (*z-scores*, *Range [-1,1]*, *Range [0,1]* and *Standard deviation of 1*), if there is no variation in the values, they will be set to zero instead.

**Standardize by** Whether to standardize by variables or cases.

**Measure transformation** Transformation of the measures. Choices include *None*, *Absolute values*, *Reverse sign* and *Range [0,1]*. For *Range [0,1]*, measures on the diagonal are ignored in the transformation.

**Show cell values** Whether to display cell values, or if this should be determined based on an estimate of available space (*Automatic*).

**Show row labels** Whether to display row labels.

**Show column labels** Whether to display column labels.

### Properties

This tab contains options for formatting the size of the object, as well as the underlying R code used to create the visualization, and the JavaScript code use to customize the *Object Inspector* itself (see Object Inspector for more details about these options). Additional options are available by editing the code.

## More Information

## Acknowledgements

Uses the `R` package `weights` and the `d3heatmap` htmlwidget.

## Code

```
form.setHeading("Distances");
formCompare = form.comboBox({name: "formCompare",
label: "Compare",
alternatives: ["Cases", "Variables"],
default_value: "Variables",
prompt: "Whether to compare cases (rows) or variables (columns)"});
if (formCompare.getValue() == "Cases")
form.dropBox({name: "formCaseLabels",
label: "Case labels",
types: ["V:text"],
required: false,
prompt: "Labels to use to refer to each case"});
form.dropBox({name: "formVariables",
label: "Variables",
types: ["V:numeric, categorical, ordered categorical"],
multi: true,
prompt: "Select variables to analyse",
height: 8});
if (formCompare.getValue() == "Variables")
form.checkBox({label: "Variable names", name: "formNames", default_value: false, prompt: "Display names instead of labels"});
form.checkBox({ name: "binaryCat", label: "Categorical as binary", default_value: false, prompt: "Code categorical variables as dummy variables"});
formMeasure = form.comboBox({name: "formMeasure",
label: "Measure",
alternatives: ["Dissimilarities", "Similarities"],
default_value: "Dissimilarities"});
if (formMeasure.getValue() == "Dissimilarities")
{
formDistance = form.comboBox({name: "formDistance",
label: "Distance measure",
alternatives: ["Euclidean", "Squared Euclidean", "Maximum", "Manhattan", "Minkowski"],
default_value: "Euclidean"});
if (formDistance.getValue() == "Minkowski")
form.numericUpDown({name: "formMinkowski",
label: "Minkowski power (p)",
default_value: 2,
minimum: 1,
maximum: 999999});
}
else
form.comboBox({name: "formSimilarity",
label: "Similarity measure",
alternatives: ["Correlation", "Cosine"],
default_value: "Correlation"});
formStandardize = form.comboBox({name: "formStandardize",
label: "Data standardization",
alternatives: ["None", "z-scores", "Range [-1,1]", "Range [0,1]", "Mean of 1", "Standard deviation of 1"],
default_value: "None",
prompt: "Options to standardize the data"});
if (formStandardize.getValue() != "None")
form.comboBox({name: "formStandardizeBy",
label: "Standardize by",
alternatives: ["Variable", "Case"],
default_value: "Case",
prompt: "Standardize by case (row) or variable (column)"});
form.comboBox({name: "formMeasureTransform",
label: "Measure transformation",
alternatives: ["None", "Absolute values", "Reverse sign", "Range [0,1]"],
default_value: "None",
prompt: "Options to transform the measure"});
form.comboBox({label: "Show cell values", name: "formCell", default_value: "Automatic",
alternatives: ["Automatic", "Yes", "No"]});
form.comboBox({label: "Show row labels", name: "formRowLabels", default_value: "Yes",
alternatives: ["Yes", "No"]});
form.comboBox({label: "Show column labels", name: "formColumnLabels", default_value: "Yes",
alternatives: ["Yes", "No"]});
```

```
library(flipDimensionReduction)
distance.matrix <- DistanceMatrix(QDataFrame(formVariables),
compare = formCompare,
case.labels = formCaseLabels,
variable.names = formNames,
binary = binaryCat,
measure = formMeasure,
similarity.measure = formSimilarity,
distance.measure = formDistance,
minkowski = formMinkowski,
standardization = formStandardize,
standardize.by = formStandardizeBy,
measure.transformation = formMeasureTransform,
show.cell.values = formCell,
show.row.labels = formRowLabels,
show.column.labels = formColumnLabels,
subset = QFilter,
weights = QCalibratedWeight)
```