# ttm: Tensor Times Matrix (m-Mode Product) In rikenbit/DelayedTensor: R package for sparse and out-of-core arithmetic and decomposition of Tensor

 ttm-methods R Documentation

## Tensor Times Matrix (m-Mode Product)

### Description

Contracted (m-Mode) product between a DelayedArray (Tensor) of arbitrary number of modes and a matrix. The result is folded back into Tensor.

### Usage

```ttm(darr, mat, m = NULL)

## S4 method for signature 'DelayedArray,DelayedArray'
ttm(darr, mat, m)
```

### Arguments

 `darr` DelayedArray object `mat` input 2D DelayedArray with same number columns as the `m`th mode of `darr` `m` the mode to contract on

### Details

This function is an extension of the `ttm` by DelayedArray.

By definition, `rs_unfold(ttm(darr, mat), m) = mat%*%rs_unfold(darr, m)`, so the number of columns in `mat` must match the `m`th mode of `darr`. For the math on the m-Mode Product, see Kolda and Bader (2009).

### Value

a DelayedArray object with K modes

### Note

The `m`th mode of `darr` must match the number of columns in `mat`. By default, the returned Tensor does not drop any modes equal to 1.

### References

T. Kolda, B. Bader, "Tensor decomposition and applications". SIAM Applied Mathematics and Applications 2009.

`rs_unfold`, `ttl`

### Examples

```library("DelayedRandomArray")
darr <- RandomUnifArray(c(2,3,4))
mat <- RandomUnifArray(c(10,4))
ttm(darr, mat, m=3)
```

rikenbit/DelayedTensor documentation built on Jan. 30, 2023, 6:15 p.m.