Tilia is a spreadsheet program designed for stratigraphic data, especially pollen data. It runs on an IBM PC, XT, AT, PS/2 or compatible. The program is user-friendly and menu-driven. Data are entered in a spreadsheet that displays the matrix of variables (pollen types or other stratigraphic variables) and samples (stratigraphic levels or other samples). The entire matrix can be accessed with the cursor keys, and the value of any cell can be entered or changed. Rows and columns can be moved, sorted, added, and deleted. Tilia stores data in an efficient binary format (the .til file), but can read and write a variety of ASCII (standard text) files.
The program calculates sums and percentages, concentrations, and accumulation rates with simple menu selections. Up to 26 sums and subsums can be calculated. Percentages can be based on any sum. From series of radiocarbon or other dates, an age for each level can be calculated with linear interpolation, cubic spline interpolation, or by fitting a polynomial.
The program also carries out cluster analysis and ordination. Cluster analysis is constrained incremental sums of squares (CONISS), known also as minimum variance, error sum of squares, and Ward's method. A number of data transformations are possible, including a square-root transformation, which results in the chord-distance dissimilarity coefficient. The analysis can be either stratigraphically constrained for quantitative zonation or unconstrained, appropriate for surface samples. Ordination procedures are correspondence analysis or detrended correspondence analysis. In addition to pollen data, this program will be useful for other ecological data, particularly in the PC environment. The program allocates memory at run time, and therefore is more flexible than the FORTRAN versions of DCA.
Tilia·graph is a companion program for producing pollen diagrams. The program can be run independently or accessed from Tilia, allowing smooth transition from spreadsheet to graphics. Tilia·graph is also user-friendly and menu-driven. Optional features include silhouette or histogram style graphs, exaggerated curves, plotting against age or depth, secondary age or depth axes, plotting positions of radiocarbon dates, zones, zone labels, ecological groups, and a CONISS dendrogram.
Tilia·graph uses the Graphical Kernel System (GKS), a device-independent, ANSI-standard, 2-D graphics package. Device independence implies that the graphics image is independent of the output device (display, printer, or plotter). A computer program called a "device driver" translates the GKS graphics image into a format appropriate for any particular output device. Tilia·graph uses a GKS graphics library and device drivers licensed from Graphic Software Systems (GSS), Inc., Beaverton, Oregon, USA. Drivers are available for most displays (Hercules monochrome and color, CGA, EGA, VGA, Super VGA, 8514/A, and others) and most printers and plotters, including dot-matrix printers, HP Laserjet, HP plotters, postscript printers, and more. The diagram can be viewed on the display and changed before being sent to the plotter or printer. The graphics output for most hardcopy devices can be optionally written to file, which can then be sent to the printer/plotter with the DOS copy command. For example, the output for an HP Laserjet can be written to a file, and then that file can be transported via floppy disk or network to a computer that is connected to a Laserjet, where it is output.
Minimum computer requirements for Tilia are DOS 2.0 or greater and 2 floppy drives. Greater functionality is possible with DOS 3.x and a hard drive. Tilia·graph requires DOS 3.0 or greater, 640 kb RAM, a hard drive, and a graphics card.
Both Tilia and Tilia·graph are available in "Beta" versions, which have most of the planned functionality. Fully functional versions should be available by the end of 1990. Tilia is available for $5 to cover mailing and floppy disks. The cost for Tilia·graph (including Tilia) is $200, which includes two GSS device drivers. Additional device drivers are available for $25 each. The GSS device drivers are licensed for a single computer. Users will require at least two device drivers, one for the display and one for a printer or plotter. Programs are available from Eric C. Grimm, Illinois State Museum, Research and Collections Center, 1920 South 10 1/2 Street, Springfield, IL, 62703, USA. [grimm@denr1.igis.uiuc.edu]
