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Explain a frame without reading numerical values

Source: R/fmri-frame.R
explain.Rd

explain() returns a bounded, serializable summary of the visible frame. Axis IDs are sampled by default so inspecting a large study does not create another large object. Set ids = "complete" only when every visible ID is required.

Usage

explain(x, ids = c("sample", "none", "complete"), sample_size = 3L)

Arguments

x

An fmri_frame or view.

ids

One of "sample", "none", or "complete".

sample_size

Number of IDs sampled from each end of each axis.

Value

A bounded serializable execution summary. No assay or aligned-block values are read. ids_durable reports whether the observation axis and the feature space carry durable IDs; when it is FALSE the semantic digest is NULL because ephemeral IDs cannot enter an FDS manifest.

Details

The schema digest describes column, block, assay, relation, entity, table, and space contracts. The semantic digest covers the complete source-free FDS manifest. Physical source fingerprints are reported separately.

Examples

sp <- volume_space(dim = c(2, 2, 2), affine = diag(4))
frame <- fmri_frame(
  assays = list(bold = matrix(rnorm(4 * n_features(sp)), nrow = 4)),
  observations = data.frame(.obs_id = sprintf("vol-%d", 1:4)),
  space = sp
)
summary <- explain(frame)
summary$shape
#> observation     feature 
#>           4           8