# Chapter 6 Centrality and Centralization

In Week 5, we explored a range of network-level measures, including `size`

, `density`

, `diameter`

, `average path length`

, `centralization`

, `reciprocity`

, `transitivity`

, `clustering coefficient`

, and so on. There are other interesting measures not covered by the textbook but worth your attention:^{10}

`Cohesion`

: The degree to which actors are connected directly to each other by cohesive bonds.`Structural cohesion`

: The minimum number of members who, if removed from a group, would disconnect the group.

You have done a phenomenonal job digging into different concepts and measures and sharing your findings back to the group via annotations. A shout-out to **HopeinJ** for asking an important question:

@bech0079, I don’t quite understand the difference btw the network.density between the network.density and edge.density, both gives the ratio between extant edges/potential edges.https://www.rdocumentation.org/packages/network/versions/1.13.0/topics/network.density Do you have any idea on that?

I want to take this opportunity to mention that there is a “universe” of R packages, the dependencies among which can be visualized as a giant graph (see this page). Among these packages, there are many packages developed for SNA. The `network`

package mentioned by **HopeinJ** is another R package that can be used for SNA. In `igraph`

, please use `[edge_density](https://www.rdocumentation.org/packages/igraph/versions/1.2.4/topics/edge_density)`

to compute network density.

Please make sure to check our Hypothes.is annotations to learn about contributions from other colleagues. If there are burning questions, please continue the discussion on Slack.

**This week, we will**:

- Engage with node-level measures in social networks
- Understand how network-level and node-level measures are connected
- Learn to calculate node-level measures using SNA applications

Note that the description of models introduced here may not fit the philosophical worldview you feel comfortable with or subscribe to. Refer back to Section @ref{threelevels} for an earlier discussion we had about aligning methodology and philosophical viewpoints.↩