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# squareform

Format distance matrix

## Syntax

Z = squareform(y)
y = squareform(Z)
Z = squareform(y,'tovector')
Y = squareform(Z,'tomatrix')

## Description

Z = squareform(y), where y is a vector as created by the pdist function, converts y into a square, symmetric format Z, in which Z(i,j) denotes the distance between the ith and jth objects in the original data.

y = squareform(Z), where Z is a square, symmetric matrix with zeros along the diagonal, creates a vector y containing the Z elements below the diagonal. y has the same format as the output from the pdist function.

Z = squareform(y,'tovector') forces squareform to treat y as a vector.

Y = squareform(Z,'tomatrix') forces squareform to treat Z as a matrix.

The last two formats are useful if the input has a single element, so that it is ambiguous whether the input is a vector or square matrix.

## Examples

```y = 1:6
y =
1   2   3   4   5   6

X = [0 1 2 3; 1 0 4 5; 2 4 0 6; 3 5 6 0]
X =
0   1   2   3
1   0   4   5
2   4   0   6
3   5   6   0```

Then squareform(y) = X and squareform(X) = y.

## See Also

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