seqLogo {TFBSTools} | R Documentation

## Plot a sequence logo

### Description

This function takes a `ICMatrix` or `TFFM` object and plot the sequence logo.

### Usage

      seqLogo(x, ic.scale = TRUE, xaxis = TRUE, yaxis = TRUE,
               xfontsize = 15, yfontsize = 15)

### Arguments

`x` | x is a valid `ICMatrix` object or `TFFM` object.
`ic.scale` | A logical value. If TRUE, the total height of one column is proportional to the information content at that position. Otherwise, all the columns will have the same height. Ignored for `TFFM` object.
`xaxis` | A logical value. If TRUE, the x-axis will be plotted. Ignored for `TFFM` object.
`yaxis` | A logical value. If TRUE, the y-axis will be plotted. Ignored for `TFFM` object.
`xfontsize` | A numeric value. The font size for x-axis.
`yfontsize` | A numeric value. The font size for y-axis.

### Details

A sequence logo is a graphical representation of the matrix model, based on the information content of each position. The information content ranges from 0 (no base preference) to 2 (only 1 base used). If `ic.scale` is TRUE, the height of the logo at certain site is proportinal to the information content value. And each stacked base (A, C, G, T)'s height is also proportional to the information content of each base at that position, and sorted based on the character size.

For a `TFFM` object, a novel graphical representation is used for capturing the dinucleotide dependencies on the TFFM. For the upper part of the sequence logo, we represent the nucleotide probabilities at position p for each possible nucleotide at position p-1. Hence, each column represents a position within a TFBS and each row the nucleotide probabilities found at that position. Each row assumes a specific nucleotide has been emitted by the previous hidden state. The intersection between a column corresponding to position p and row corresponding to nucleotide n gives the probabilities of getting each nucleotide at position p if n has been seen at position p-1. The opacity to represent the sequence logo is proportional to the probablity of possible row to be used by the TFFM.

### Value

No return value.

### Note

This function is based on the function `seqLogo` from the Bioconductor package `seqLogo`, especially for the plotting code of TFFM.

### Author(s)

Ge Tan

### References

T D Schneider, R. M. S. (1990). Sequence logos: a new way to display consensus sequences. Nucleic acids research, 18(20), 6097.

Mathelier, A., and Wasserman, W.W. (2013). The next generation of transcription factor binding site prediction. PLoS Comput. Biol. 9, e1003214.

### See Also

`toICM`, `ICMatrix`,

### Examples

      ## ICMatrix
      data(MA0003.2)
      icm = toICM(MA0003.2)
      seqLogo(icm, ic.scale = TRUE)

      ## TFFM
      xmlFirst <- file.path(system.file("extdata", package="TFBSTools"),
                            "tffm_first_order.xml")
      tffmFirst <- readXMLTFFM(xmlFirst, type="First")
      seqLogo(tffmFirst)

[Package TFBSTools version 1.18.0 Index]