BANDITS_test-class {BANDITS} | R Documentation

## BANDITS_test class

### Description

`BANDITS_test` contains the results of the differential transcript usage (DTU) test. `BANDITS_test` is organized in three data.frames containing: gene-level results, transcript-level results and convergence diagnostics of the Markov chain Monte Carlo (MCMC) posterior chains. Created via `test_DTU`. To test for convergence, we use Heidelberger and Welch's convergence diagnostic, implemented in `coda::heidel.diag`, to test for the stationarity of the chain for the full log-posterior density; we use a 0.01 threshold on the p.value to reject the null hypotehsis of stationarity.

### Usage

    ## S4 method for signature 'BANDITS_test'
    show(object)

    ## S4 method for signature 'BANDITS_test'
    convergence(x)

    ## S4 method for signature 'BANDITS_test'
    top_genes(x, n = Inf, sort_by_g = "p.value")

    ## S4 method for signature 'BANDITS_test'
    top_transcripts(x, n = Inf,
      sort_by_tr = "gene")

    ## S4 method for signature 'BANDITS_test'
    gene(x, gene_id)

    ## S4 method for signature 'BANDITS_test'
    transcript(x, transcript_id)

    ## S4 method for signature 'BANDITS_test'
    plot_proportions(x, gene_id, CI = TRUE,
      CI_level = 0.95)

### Arguments

`object, x` | a 'BANDITS_test' object.
`n` | the number of genes or transcripts to report. By default `n = Inf` and all results will be reported.
`sort_by_g` | "p.value" for sorting results according to gene-level significance (i.e., p.value); "DTU_measure" for sorting results according to the 'DTU_measure' (check the vignette for details).
`sort_by_tr` | "gene" for sorting results according to gene-level significance (i.e., p.value); "transcript" for sorting results according to transcript-level significance (i.e., p.value).
`gene_id` | a character string or vector indicating the gene or genes whose results should be retrieved.
`transcript_id` | a character string or vector indicating the transcript or transcripts whose results should be retrieved.
`CI` | a logical element indicating whether to also plot confidence boundaries (TRUE) or not (FALSE).
`CI_level` | a number between 0 and 1, indicating the level of the confidence interval to plot.

### Value

- `show(object)`: prints the number of gene and transcript level results in the `BANDITS_test` object.

- `top_genes(x, n = Inf, sort_by_g = "p.value")`: returns the gene-level results of the DTU test for the top 'n' significant genes. By default n = Inf and all results will be reported. sort_by_g = "gene" for sorting results according to gene-level significance; sort_by_g = "DTU_measure" for sorting results according to the 'DTU_measure'.

- `top_transcripts(x, n = Inf, sort_by_tr = "gene")`: returns the transcript-level results of the DTU test for the top 'n' significant genes. By default n = Inf and all results will be reported. sort_by_tr = "gene" for sorting results according to gene-level significance; sort_by_tr = "transcript" for sorting results according to transcript-level significance.

- `convergence(x)`: returns the convergence diagnostic of the posterior MCMC chains for every gene.

- `gene(x, gene_id)`: returns a list with all results for the gene(s) specified in 'gene_id': gene results, corresponding transcript results and convergence diagnostic.

- `transcript(x, transcript_id)`: returns a list with all results for the trancript specified in 'transcript_id': transcript results, corresponding gene results and convergence diagnostic.

- `plot_proportions(x, gene_id, CI = TRUE, CI_level = 0.95)`: plots the posterior means of the average transcripts relative expression (i.e., the proportions) of each condition, for the gene specified in 'gene_id'. If 'CI' is TRUE, a profile Wald type confidence interval will also be plotted for each transcript estimated proportion; the level of the confidence interval is specified by 'CI_level'.

### Slots

`Gene_results`

  a `data.frame` containing the gene-level results of the DTU test, structured in the following columns:

  - Gene_id contains the gene names;

  - p.values is the gene-level p.values of the DTU test;

  - adj.p.values is the Benjamini-Hochberg adjusted p.values (via `p.adjust`);

  - p.values_inverted (only available for 2-group comparisons) is a conservative p.value, accounting for the inversion of the dominant transcript between conditions: p.values_inverted = p.values, if the dominant transcript varies between conditions, and p.values_inverted = sqrt( p.values ) if both conditions have the same dominant transcript;

  - adj.p.values_inverted (only available for 2-group comparisons) is the Benjamini-Hochberg adjusted p.values_inverted, via `p.adjust`;

  - DTU_measure (only available for 2-group comparisons) represents a measure of the intensity of changes between conditions. This measure ranges between 0, when proportions are identical between groups, and 2, when an isoform is always expressed in group A and a different transcript is always chosen in group B;

  - Mean log-prec "group_name" indicates the posterior mean of the logarithm of the Dirichlet precision parameter in group "group_name". The precision parameter models the degree of over-dispersion between samples: the higher the precision parameter (or its logarithm), the lower the sample-to-sample variability.

  - SD log-prec "group_name" indicates the standard deviation of the logarithm of the Dirichlet precision parameter in group "group_name".

`Transcript_results`

  a `data.frame` containing the transcript-level results of the DTU test, structured in the following columns:

  - Gene_id contains the gene names;

  - Transcript_id contains the transcript names;

  - p.values is the transcript-level p.values of the DTU test;

  - adj.p.values is the Benjamini-Hochberg adjusted p.values (via `p.adjust`);

  - Max_Gene_Tr.p.val is a conservative p.value and represents the maximum between the transcript p.value and corresponding gene p.value;

  - Max_Gene_Tr.Adj.p.val is the Benjamini-Hochberg adjusted Max_Gene_Tr.p.val (via `p.adjust`);

  - Mean "group_name" indicates the posterior mean of the average relative abundance of the transcript in group "group_name" (an `NaN` value indicates that no data was available for a group to estimate parameters);

  - SD "group_name" indicates the standard deviation of the average relative abundance of the transcript in group "group_name" (an `NaN` value indicates that no data was available for a group to estimate parameters); this column indicates the variability in the mean estimate and is used to plot a Wald type confidence interval for the mean relative abundance via `plot_proportions`.

`Convergence`

  a `data.frame` containing the convercence diagnostics of the DTU test, structured in the following columns:

  - Gene_id contains the gene names;

  - converged is 1 if convergence was reached, 0 otherwise;

  - burn_in indicates what fraction of the chain was removed to ensure convergence (excluding the `burn_in` parameter specified in `test_DTU`.

`samples_design`

  a `data.frame` containing the design of the experiment, with one row for each sample and two columns with names 'sample_id' and 'group', specifying the id and group of each sample, respectively. It is provided by the user to `test_DTU`.

### Author(s)

Simone Tiberi simone.tiberi@uzh.ch

### See Also

`test_DTU`, `create_data`, `BANDITS_data`

### Examples

    # load the pre-computed results:
    data("results", package = "BANDITS")
    show(results)

    # Visualize the most significant Genes, sorted by gene level significance.
    head(top_genes(results))

    # Alternatively, gene-level results can also be sorted according to DTU_measure,
    # which is a measure of the strength of the change between the
    # average relative abundances of the two groups.
    head(top_genes(results, sort_by = "DTU_measure"))

    # Visualize the most significant transcripts, sorted by transcript level significance.
    head(top_transcripts(results, sort_by = "transcript"))

    # Visualize the convergence output for the most significant genes,
    # sorted by gene level significance.
    head(convergence(results))

    # We can further use the 'gene' function to gather all output for a specific gene:
    # gene level, transcript level and convergence results.
    top_gene = top_genes(results, n = 1)
    gene(results, top_gene$Gene_id)

    # Similarly we can use the 'transcript function to gather all output
    # for a specific transcript.
    top_transcript = top_transcripts(results, n = 1)
    transcript(results, top_transcript$Transcript_id)

    #Finally, we can plot the estimated average transcript relative expression
    # in the two groups for a specific gene via 'plot_proportions'.
    plot_proportions(results, top_gene$Gene_id)

[Package BANDITS version 1.8.0 Index]