export-funs {FELLA} | R Documentation

## Generate and manipulate tables and sub-networks from an enrichment

### Description

In general, `generateResultsTable`, `generateEnzymesTable` and `generateResultsGraph` provide the results of an enrichment in several formats.

Function `generateResultsTable` returns a table that contains the best hits from a `FELLA.USER` object with a successful enrichment analysis. Similarly, `generateEnzymesTable` returns a data frame with the best scoring enzyme families and their annotated genes.

Function `generateResultsGraph` gives a sub-network, plottable through `plotGraph`, witht the nodes with the lowest `p.score` from an enrichment analysis. Function `addGOToGraph` can be applied to such sub-networks to overlay GO labels and similarity to a user-defined GO term.

Function `exportResults` is a wrapper around `generateResultsTable`, `generateEnzymesTable` and `generateResultsGraph` to write the results to files.

### Usage

    generateResultsTable(method = "diffusion", threshold = 0.05,
        plimit = 15, nlimit = 250, LabelLengthAtPlot = 45,
        capPscores = 1e-06, object = NULL, data = NULL, ...)

    generateEnzymesTable(method = "diffusion", threshold = 0.05,
        nlimit = 250, LabelLengthAtPlot = 45, capPscores = 1e-06,
        mart.options = list(biomart = "ensembl", dataset =
        "hsapiens_gene_ensembl"), object = NULL, data = NULL, ...)

    generateResultsGraph(method = "diffusion", threshold = 0.05,
        plimit = 15, nlimit = 250, thresholdConnectedComponent = 0.05,
        LabelLengthAtPlot = 22, object = NULL, data = NULL, ...)

    exportResults(format = "csv", file = "myOutput",
        method = "diffusion", object = NULL, data = NULL, ...)

    addGOToGraph(graph = NULL, GOterm = NULL, godata.options = list(OrgDb
        = "org.Hs.eg.db", ont = "CC"), mart.options = list(biomart = "ensembl",
        dataset = "hsapiens_gene_ensembl"))

    plotGraph(graph = NULL, layout = FALSE, graph.layout = NULL,
        plotLegend = TRUE, plot.fun = "plot.igraph", NamesAsLabels = TRUE,
        ...)

### Arguments

`method` | one in `"diffusion"`, `"pagerank"`
`threshold` | Numeric value between 0 and 1. `p.score` threshold applied when filtering KEGG nodes. Lower thresholds are more stringent.
`plimit` | Pathway limit, must be a numeric value between 1 and 50. Limits the amount of pathways in `method = "hypergeom"`
`nlimit` | Node limit, must be a numeric value between 1 and 1000. Limits the order of the solution sub-graph when in `method = "diffusion"` and `method = "pagerank"`
`LabelLengthAtPlot` | Numeric value between 10 and 50. Maximum length that a label can reach when plotting the graph. The remaining characters will be truncated using "..."
`capPscores` | Numeric value, minimum p-score admitted for the readable formatting. Smaller p-scores will be displayed as `< capPscores`
`object` | FELLA.USER object
`data` | FELLA.DATA object
`...` | Optional arguments for the plotting function in `plotGraph`. Arguments passed to the exporting function in `exportResults`. Ignored otherwise.
`mart.options` | List, options for the `biomaRt` function `getBM`. Importantly, this defines the organism, see `listDatasets` for possibilities. If calling `generateEnzymesTable`, the user can set `mart.options = NULL` to avoid adding GO labels to enzymes.
`thresholdConnectedComponent` | Numeric value between 0 and 1. Connected components that are below the threshold are kept, while the ones exceeding it (because they are too small) are discarded.
`format` | Character, one of: `"csv"` for regular results table, `"enzyme"` for table with enzyme data, `"igraph"` for igraph format. Alternatively, any format supported by igraph, see `write_graph`
`file` | Character specifying the output file name
`graph` | An igraph object, typically a small one, coming from an enrichment through `"diffusion"` or `"pagerank"`.
`GOterm` | Character, GO entry to draw semantic similarity in the solution graph. If `NULL`, the GO labels will be appended without similarities.
`godata.options` | List, options for the database creator `godata`
`layout` | Logical, should the plot be returned as a layout?
`graph.layout` | Two-column numeric matrix, if this argument is not null then it is used as graph layout
`plotLegend` | Logical, should the legend be plotted as well?
`plot.fun` | Character, can be either `plot.igraph` or `tkplot`
`NamesAsLabels` | Logical, should KEGG names be displayed as labels instead of KEGG identifiers?

### Details

Functions `generateResultsTable` and `generateEnzymesTable` need a `FELLA.DATA` object and a `FELLA.USER` object with a successful enrichment. `generateResultsTable` provides the entries whose p-score is below the chosen `threshold` in a tabular format. `generateEnzymesTable` returns a table that contains (1) the enzymes that are below the user-defined p-score threshold, along with (2) the genes that belong to the enzymatic families in the organism defined in the database, and (3) GO labels of such enzymes, if `mart.options` is not `NULL` and points to the right database.

Function `generateResultsGraph` returns an igraph object with a relevant sub-network for manual examination. A `FELLA.USER` object with a successful enrichment analysis and the corresponding `FELLA.DATA` must be supplied. Graph nodes are prioritised by `p.score` and selected through the most stringent between (1) p.score `threshold` and (2) maximum number of nodes `nlimit`.

There is an additional filtering feature for tiny connected components, controllable through `thresholdConnectedComponent` (smaller is stricter). The user can choose to turn off this filter by setting `thresholdConnectedComponent = 1`. The idea is to discard connected components so small that are likely to arise from random selection of nodes. Let `k` be the order of the current sub-network. A connected component of order `r` will be kept only if the probability that a random subgraph from the whole KEGG knowledge model of order `k` contains a connected component of order at least `r` is smaller than `thresholdConnectedComponent`. Such probabilities are estimated during `buildDataFromGraph`; the amount of random trials can be controlled by its `niter` argument.

Function `exportResults` writes the enrichment results as the specified filetype. Options are: a csv table (`"csv"`), an enzyme csv table (`"enzyme"`) an igraph object as an `RData` file, or any format supported by igraph's `write_graph`.

Function `addGOToGraph` takes and returns a graph object with class igraph adding the following attributes: GO labels in `V(graph)$GO`, and semantic similarities in `V(graph)$GO.simil` if `GOterm != NULL`.

The GO database describes genes in terms of three ontologies: molecular function (MF), biological process (BP) and cellular component (CC) [Gene Ontology Consortium, 2015]. The user can be interested in finding which enzymatic families reported with a low `p.score` are closest to a particular GO term. To assess similarity between GO labels, FELLA uses the semantic similarity defined in [Yu, 2010] and their implementation in the GOSemSim R package. The user will obtain, for each enzymatic family, the closest GO term to his or her GO query and the semantic similarity between them. Exact matches have a similarity of `1`. Function `plotGraph` detects the presence of the GO similarity option and plots its magnitude.

Function `plotGraph` plots a solution graph from the diffusion and pagerank analysis. For plotting hypergeom results, please use `plot` instead. Specific colors and shapes for each KEGG category are used: pathways are maroon, modules are violet, enzymes are orange, reactions are blue and compounds are green. If the graph contains the similarity to a GO term, enzymes will be displayed as triangles whose color depicts the strength of such measure (yellow: weak, purple: strong). At the moment, `plotGraph` allows plotting throug the static `plot.igraph` and the interactive `tkplot`.

### Value

`generateResultsTable` returns a data.frame that contains the nodes below the `p.score` threshold from an enrichment analysis

`generateEnzymesTable` returns a data.frame that contains the enzymes below the `p.score` threshold, along with their genes and GO labels

`generateResultsGraph` returns an igraph object: a sub-network from the whole KEGG knowledge model under the specified thresholds (`threshold` and `thresholdConnectedComponent`)

`exportResults` returns `invisible()`, but as a side effect the specified `file` is created.

`addGOToGraph` returns an igraph object, which is the input `graph` with extra attributes: GO labels in `V(graph)$GO`, and semantic similarities in `V(graph)$GO.simil` if `GOterm != NULL`

`plotGraph` returns `invisible()` if `layout = F` and the plotting layout as a data.frame otherwise.

### References

Gene Ontology Consortium. (2015). Gene ontology consortium: going forward. Nucleic acids research, 43(D1), D1049-D1056.

Yu, G., Li, F., Qin, Y., Bo, X., Wu, Y., & Wang, S. (2010). GOSemSim: an R package for measuring semantic similarity among GO terms and gene products. Bioinformatics, 26(7), 976-978.

### Examples

    ## First generate a toy enrichment
    library(igraph)
    data(FELLA.sample)
    data(input.sample)
    ## Enrich input
    obj <- enrich(
    compounds = input.sample,
    data = FELLA.sample)

    ######################
    ## Results table
    tab.res <- generateResultsTable(
    method = "hypergeom",
    threshold = 0.1,
    object = obj,
    data = FELLA.sample)
    head(tab.res)

    tab.res <- generateResultsTable(
    method = "diffusion",
    threshold = 0.1,
    object = obj,
    data = FELLA.sample)
    head(tab.res)

    ######################
    ## Use wrapper to write the table to a file
    out.file <- tempfile()
    exportResults(
    format = "csv",
    threshold = 0.1,
    file = out.file,
    object = obj,
    data = FELLA.sample)
    tab.wrap <- read.csv(out.file)
    head(tab.wrap)

    ######################
    ## Enzymes table
    tab.ec <- generateEnzymesTable(
    threshold = 0.1,
    object = obj,
    data = FELLA.sample,
    mart.options = NULL)
    head(tab.ec)

    ######################
    ## Generate graph
    g.res <- generateResultsGraph(
    method = "pagerank",
    threshold = 0.1,
    object = obj,
    data = FELLA.sample)
    g.res

    ## Plot graph (without GO terms)
    plotGraph(g.res)

    ## Add similarity to the GO CC term "mitochondrion"
    ## Not run:
    g.cc <- FELLA:::addGOToGraph(
    graph = g.res,
    GOterm = "GO:0005739")

    ## Plot graph (with GO terms)
    plotGraph(g.cc)

    ## Without the CC
    any(V(g.res)$GO.simil >= 0)
    ## With the CC
    v.cc <- unlist(V(g.cc)$GO.simil)
    sum(v.cc >= 0, na.rm = TRUE)
    ## Similarity values
    table(v.cc)

    ## End(Not run)

[Package FELLA version 1.4.1 Index]