igraph Reference Manual Gábor Csárdi Department of Biophysics, Research Institute for Nuclear and Particle Physics of the Hungarian Academy of Sciences 29-33 Konkoly-Thege Miklós road, Budapest H-1121, Hungary Center for Complex Systems Studies, Kalamazoo College 1200 Academy st, Kalamazoo, 49006, MI, USA Tamás Nepusz Department of Biophysics, Research Institute for Nuclear and Particle Physics of the Hungarian Academy of Sciences 29-33 Konkoly-Thege Miklós road, Budapest H-1121, Hungary igraph Reference Manual by Gábor Csárdi and Tamás Nepusz Copyright (C) 2005, 2006 Gábor Csárdi and Tamás Nepusz. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation License”. Table of Contents 1. Introduction............................................................................................................................................1 1.1. igraph is free software.................................................................................................................1 1.2. Citing igraph...............................................................................................................................2 2. Installation..............................................................................................................................................3 3. Tutorial...................................................................................................................................................5 3.1. Lesson 1. Compiling programs using igraph..............................................................................5 3.2. Lesson 2. Creating your first graphs...........................................................................................6 3.3. Lesson 3. Calculating various properties of graphs....................................................................8 4. About igraph graphs, the basic interface..........................................................................................10 4.1. The igraph data model...............................................................................................................10 4.2. The basic interface....................................................................................................................11 4.2.1. Graph Constructors and Destructors............................................................................11 4.2.2. Basic Query Operations................................................................................................14 4.2.3. Adding and Deleting Vertices and Edges.....................................................................20 5. Error Handling....................................................................................................................................25 5.1. Error handling basics................................................................................................................25 5.2. Error handlers............................................................................................................................25 5.2.1. igraph_error_handler_t — Type of error handler functions...............................25 5.2.2. igraph_error_handler_abort — Abort program in case of error.......................26 5.2.3. igraph_error_handler_ignore — Ignore errors.................................................26 5.2.4. igraph_error_handler_printignore — Print and ignore errors.......................27 5.3. Error codes................................................................................................................................27 5.3.1. igraph_error_type_t — Error code type..............................................................27 5.3.2. igraph_strerror — Textual description of an error...............................................30 5.4. Advanced topics........................................................................................................................31 5.4.1. Writing error handlers..................................................................................................31 5.4.2. Error handling internals................................................................................................32 5.4.3. Deallocating memory...................................................................................................34 5.4.4. Writing igraph functions with proper error handling..................................................35 5.4.5. Error handling and threads...........................................................................................36 6. Data structure library: vector, matrix, other data types..................................................................37 6.1. About template types................................................................................................................37 6.2. Vectors.......................................................................................................................................38 6.2.1. About igraph_vector_t objects......................................................................................38 6.2.2. Constructors and Destructors.......................................................................................39 6.2.3. Initializing elements.....................................................................................................42 6.2.4. Accessing elements......................................................................................................43 6.2.5. Vector views.................................................................................................................47 6.2.6. Copying vectors............................................................................................................48 6.2.7. Exchanging elements....................................................................................................50 6.2.8. Vector operations..........................................................................................................51 6.2.9. Finding minimum and maximum.................................................................................55 6.2.10. Vector properties.........................................................................................................59 6.2.11. Searching for elements...............................................................................................63 iii 6.2.12. Resizing operations....................................................................................................66 6.2.13. Sorting........................................................................................................................71 6.2.14. Pointer vectors (igraph_vector_ptr_t).........................................................................71 6.3. Matrices.....................................................................................................................................77 6.3.1. About igraph_matrix_t objects.....................................................................................77 6.3.2. Matrix constructors and destructors.............................................................................77 6.3.3. Initializing elements.....................................................................................................79 6.3.4. Copying matrices..........................................................................................................80 6.3.5. Accessing elements of a matrix....................................................................................82 6.3.6. Operations on rows and columns..................................................................................84 6.3.7. Matrix operations..........................................................................................................90 6.3.8. Combining matrices......................................................................................................96 6.3.9. Finding minimum and maximum.................................................................................97 6.3.10. Matrix properties......................................................................................................101 6.3.11. Searching for elements.............................................................................................105 6.3.12. Resizing operations..................................................................................................107 6.4. Sparse matrices.......................................................................................................................110 6.4.1. About igraph_spmatrix_t objects...............................................................................110 6.4.2. Sparse matrix constructors and destructors................................................................111 6.4.3. Accessing elements of a sparse matrix.......................................................................112 6.4.4. Matrix query operations.............................................................................................114 6.4.5. Matrix operations........................................................................................................117 6.5. Stacks......................................................................................................................................120