6 Network analysis
Mapping
Use the Network >> mapping module to create features to modify the network map bode and edge properties.
The following is an example of how to format and combine analysis for network mapping. Check out the user manual for more details about this module’s features.
Methods
Use the transformation
map fold change
to format fold-change values (e.g. FC_
results from the statistics module). This will create separate features for FC_
magnitude(log2) and direction of change.
Select calculate
and save
to add the created features to the global data set.
Use a similar procedure to format p-values
and combine features.
Use map p-value
to evaluate an inequqlity
comparing a variable to a threshold
value.
Use combine columns
to concatenate variables multiple variables into a single feature. Note, save the created variables from map fold change
and map p-value
transformations
before using in the combine columns
transformation
.
Select calculate
to view the results then use save
to add the created features to the global data set.
Correlation analysis
Use the Network >> correlation module to calculate regularized correlations among all variables.
First, define the correlation method
and p-value
significance threshold and then select calculate
.
Next, use regularize to prune the network to maintain the most confident relationships. Use optimization
to define the initial method (ric
or stars
Jiang et al. (2019)). Next, you can select the manual
optimization and select a custom regularization lambda
(the higher the more strict the selection).
Select calculate
and view the method results.
Explore and plot
For example the following mapped network displays positive and negative regularized correlations and the following node properties:
- size = magnitude of fold-change
- color and shape = direction of fold change and if the statistical p-value met the threshold criteria set in mapping.
The edges have been filtered to retain Tanimoto similarity > 0.8. See the user manual for more details about how to customize the visualization.
Use save to add the calculate network as an option to integrate with other available networks for the data set in network >> enrich.
Biochemical network
Use the Network >> biochemical module to calculate biochemical (substrate to product) relationships for all KEGG
ids for metabolite measurements.
Define which variable in the data corresponds to the KEGG
id or first use the network >> translate to translate it from metabolite names or other identifiers.
Next, visualize
, create a report
and save the calculated network.
Structural similarity network
Use the Network >> structural module to calculate molecule structural similarity relationships for all PubChem CID
ids for metabolite measurements.
Define which variable in the data corresponds to the CID
id or first use the network >> translate to translate it from metabolite names or other identifiers.
Next, visualize
, create a report
and save the calculated network.
Network enrichment
Use the Network >> enrich module to combine, update and visualize the calculated networks.
Select networks which should be combined into a single network. Note, selecting single edges
removes any duplicated connections keeping the first observed instance as defined by the order of the selected networks
.
Visualize
, create a report
and save the calculated network.
For example, the following interactive
network displays the combined biochemical
, correlation
and structural similarity
connections. The node size shows the magnitude of the fold change between classes
. Node color encodes the direction and significance of the fold changes.
You can zoom and pan in the network and use the legend to filter the visualized nodes and edges. For example, the following subnetwork shows nodes for all significantly altered comparisons.
Save and export
Save the created network to make it available for export.
To continue optimizing the network using external tools, use the data module to export (save) the selected network nodes
and edges
.
Grapov, D., K. Wanichthanarak, and O. Fiehn. 2015. “MetaMapR: Pathway Independent Metabolomic Network Analysis Incorporating Unknowns.” Journal Article. Bioinformatics 31 (16): 2757–60. https://doi.org/10.1093/bioinformatics/btv194.
Jiang, Haoming, Xinyu Fei, Han Liu, Kathryn Roeder, John Lafferty, Larry Wasserman, Xingguo Li, and Tuo Zhao. 2019. Huge: High-Dimensional Undirected Graph Estimation. https://CRAN.R-project.org/package=huge.