Gnuplot. in Action. Understanding Data with Graphs MANNING. (74 w. long.) PHILIPP K. JANERT. Greenwich

Transcription

1 Gnuplot in Action Understanding Data with Graphs PHILIPP K. JANERT 11 MANNING Greenwich (74 w. long.)

2 contents foreword xvii foreword xix prreface xxi acknowledgments xxiii about this book xxv pajrlt X ^Basics ««*«««»««*«««**««sf«*«*»««*»»«a««**««ttt«*««*»*«*«*«l "1 Prelude: Understanding data with gnuplot 3 -*~ 1.1 A busy weekend 4 Planning a marathon 4 Determining the future What is graphical analysis? 9 Data analysis and visualization concepts 10 * Why graphical analysis? 12 * Limitations of graphical analysis What is gnuplot? 13 Gnuplot isn't GNU 13» Why gnuplot? 14 «Limitations Summary 15

3 9 Essential gnuplot Simple plots 16 Invoking gnuplot and first plots 17 * Plotting data from a file 20 * Abbreviations and defaults Saving and exporting 24 Saving and loading commands 25 Exporting graphs 25 One-step export script Summary 28 88% J Working with data Managing large data sets 30 Multiple data sets perfile: index lines: every 31 30* Records spanning multiple 3.2 Smoothing and summarizing data 32 Plotting unsorted data files 32 * Smoothing noisy 3.3 Math with gnuplot 38 Mathematical expressions 38 * Built-in functions 38 data 35 User-defined variables and functions 39 * Complex numbers Data transformations 41 Simple data transformations 41 * Pseudocolumns and the column function Plotting functions and data 43 Tricks and warnings Logarithmic plots 44 How do logarithmic plots 3.7 Summary 47 work? 44 4 Practical matters Managing options Data files 51 Permissible formats and options Strings 55 Quotes 55 String operations 55 * String applications 57 Crazy example: plotting the Unix password file Generating textual output 59 The print command 59* The set table option 60

4 4.5 Interacting with gnuplot 61 Getting help 61 * Command history 61 * Hot keys and mousing 62» Reading data interactively Summary 64 J^AJR.T 2 I^OLISHIISifCT i«««i«tii«ii>«4himfttd(«t»t«>ai«i«t»(iit«ieh<htittii«65 Doing it with style Choosing plot styles 68 Inline style directives 68 Terminal capabilities 69 Global style directives Plot styles 70 Core styles 71 Box styles 72 Styles with errorbars or ranges 78 Filled styles 81 Other styles Customizing styles 85 Custom line styles 86 * Specifying color 87 Worked example: half-tone shading Summary 89 Decorations Quick start: minimal context for data Digression: locations on a graph Additional graph elements: decorations 94 Common conventions 94 «Arrows 94 Text labels 97 Objects The graph's legend or key 100 Turning the key on and off 101 Placement 101 Layout 101 Explanations 102 * Appearance 104 Default settings Worked example: features of a spectrum Overall appearance 106 Size and aspect ratio 106 Borders and margins Summary 109 7All about axes Multiple axes 111 Terminology 111 Plotting with two coordinate systems 112 Should you doit? 113

5 Selecting plot ranges Tic marks Major tic marks 116 Minor tic marks 117 * * Formatting the tic labels 118* Reading tic labels from file 122 Grid and zero axes A worked example Special case: time series 124 Turning numbers into names: months and weekdays 124 General time series: the gory details Summary 130 Part 3 Advanced Gnuplot 131 Three-dimensional plots Basics Options for surface and contour plots 136 Surface plots 136 * Contour lines Coordinate axes and view point 141 Borders 142 * Viewpoint Plotting data from a file using splot 145 Grid format 146 * Matrix format 148 * Smooth surfaces Summary 151 Color Defining palettes 153 Color spaces: a refresher 153* The palette option Creating colored graphs with palettes 157 Thepm3d mode 157* The colorbox 158* Other ways to use color Using color for data representation 161 Thoughts on palette design 162 * Some sample palettes 165 Words of caution Case studies 169 A smoothly varyingfunction 169 * A complex figure Summary 173

6 Advanced plotting concepts Multiple* 176 Regular arrays ofgraphs with layout 177 «Graphs within a graph 179 Graphs aligned 10.2 Higher math and special on a common axis 181 occasions 183 Parametric plots 183 Non-Cartesian coordinates 184 Vector fields Curve fitting 190 Background 190 Using the fit command 191 * Worked example 195 Should you do it? Summary 199 Terminals in depth Exporting graphs to file Common, terminal options 202 Size 202 * Fonts 202 Enhanced text mode 202 Miscellaneous appearance options 205 Flushing output channels Standard graphics file formats 206 Bitmaps SVG Print-quality output 209 PostScript 209 * Using PostScript plots with LaTeX 211 PDF Interactive terminals 218 wxt 218 xll 219 aqua 219 * windows Other terminals Summary 221 Macros, scripting, and batch operations Strings and string macros Calling other programs from gnuplot 224 Executing a command in a subshell 225 Capturing the output of asubprocess 225 Input/output redirection (Unix only) 226 Example: watermarking plots Calling gnuplot from other programs 228 Batch operations 228 Invoking gnuplotfrom other programs 229 * Example: creating a font table 232

7 12.4 Slideshows with pause and reread Configuring your workspace 234 Creating custom hot key bindings Gnuplot for the web 239 Using Gnuplot as a CGI script 239 * Using gnuplot as a subprocess to a CGI script Summary 241 Part 4 Graphical Analysis with Gnuplot Fundamental graphical methods Relationships 246 Scatter plots 246 * Logarithmic scales Counting statistics 256 Jitter plots and histograms 256 * Kernel density estimates 258 Cumulative distribution functions 259 Consider using median and percentiles Ranked data Multivariate data 264 Parallel coordinate plots 264 * Multivariate analysis 269 Star plots 270 * Historical perspective: computer-aided data analysis Summary Techniques ofgraphical analysis The core principle of graphical analysis Iteration and transformation 275 A case study in iteration: car data 275 * Making data comparable: monitoring quantities in a control chart 278 * Honor the data: truncation and responsiveness Changing the appearance to improve perception 284 Banking 284 Judging lengths * and distances 287 Enhancing quantitative perception 289* Plot ranges and the matter of zero 291 * A tough problem: the display of changing compositions 292

8 14.4 Housekeeping 296 The lifecycle of a graph 296 Input data files * 296 Output files Reminders for presentation graphics Summary 300 Coda: Understanding data with graphs 301 appendix A Obtaining, building, and installing gnuplot 303 appendix B Gnuplot reference 309 appendix C Resources 345 index 351