Input files

mplot requires two input files, with extensions plp and plt .

The file with extension plp contains plot parameters such as axis lengths, titles, labels etc, whereas the other file, with extension plt , contains the actual data values to be plotted. Both files are formatted ASCII files, and it is therefore possible to change the layout of the plots by editing the plp file.

A typical plp file is:

     1024                                 MODULO
_FIPP__STLDAV,CPX,IYA	
_DEPTH AVERAGED LOSS	
_SAFARI-FIP case 3.	
_       2                                 NUMBER OF LABELS 
_Freq:   30.0 Hz$
_SD:     50.0 m$
_      20.000000                          XLEN	
_      12.000000                          YLEN	
_       0                                 GRID TYPE	
_    0.000000                             XLEFT	
_     5.00000                             XRIGHT	
_     1.00000                             XINC	
_     1.00000                             XDIV	
_Range (km)$	
_LIN		
_     80.0000                             YDOWN	
_     20.0000                             YUP
_     10.0000                             YINC
_     1.00000                             YDIV
_Normal stress (dB//1Pa)$
_LIN				
_        1                                NC
_      112                                N	
_        0.044957                         XMIN	
_    0.449567-001                         DX	
_    0.000000                             YMIN
_        0.000000                         DY
_FIP___PLTEND

The underscore denotes a space which is necessary for mplot to correctly read the file. The plp file will always start with a block size MODULO, with which the corresponding data file was written. This parameter is a leftover from the versions using binary data files, but for the present version of mplot this parameter is dummy. The file ends with the PLTEND flag signalling the end-of-file.

Between these two records the blocks of actual plot parameters are specified, in the present case for a single plot only. Any number of blocks could, however, be included, each generating one plot.

The plot parameter block starts with a record specifying a 12-character plot identification (FIPP STLDAV) followed by a series of 3-character options separated by commas. The files generated by the acoustic propagation models will in general not have any options specified, but these are important tools for generating final plots. The following options are currently available:

DUP

A DUPLEX character generator will be used in stead of the default SIMPLEX.

CPX

The COMPLEX character generator is selected.

ITA

The ITALIC character generator is used.

IXA

Integer format will be used for plotting the x-axis tick mark numbers instead of the default decimal format.

IYA

Integer format will be used for plotting the y-axis tick mark numbers instead of the default decimal format.

DSD

If the plot contains more than one curve (NC>1), then the first curve will be plotted with a solid line, the second with a dashed and the third with a dotted. If more than three curves are plotted, this sequence will be repeated.

COL

This option will plot individual curves in different colour, using the repeatable sequence: red - green - blue - cyan - magenta - yellow. Also affects the shading option SHD .

MRK

A marker will be plotted for each 10th data point on the curves. In the case of more curves, different markers will be used for each.

TCT

This option is used in connection with the stacked time series plots in order to truncate the amplitude of each trace at an amplitude corresponding to half the distance between traces.

SHD

Produces shaded wiggles on timeseries plots. If specified alone both positive and negative wiggles will be shaded. If specified together with options POS or NEG only the positive or negative wiggles will be shaded, respectively. If specified together with COL the shading is color coded depending on the amplitude. Currently the shading will only appear on the hardcopy devices.

POS

Shading only applied to positive wiggles.

NEG

Shading only applied to negative wiggles.

NWR

Disables plotting of the option at the upper right corner of the plot. Used when generating final figures for documents.

NOP

This option will read both the parameters from the plp file and the data from the plt file but no plot is produced. It is therefore used for time saving when only selected plots are required.

The next record specifies the main title of the plot, followed by a record containing the title specified in the data file for the propagation models. This title will be plotted just above the plot frame.

There is then a sub-block containing the labels to be plotted in the upper right corner of the plot frame. The number of labels () is given first, followed by the label texts, each of which should be on separate lines and terminated by a $.

The parameters XLEN and YLEN specify the length in cm of the x- and y-axis, respectively. The parameter labelled GRID TYPE indicates whether a grid should be plotted. A value of 1 will produce a dotted grid.

The next 6 records contain the parameters for the x-axis of the plot. XLEFT and XRIGHT are the data values at the left and right borders of the plot frame, respectively, whereas XINC is the distance in the same units between the tick marks. XDIV is a multiplication factor which will be applied to both the axis parameters and the data values. After XDIV the x-axis label is specified, terminated by a $, and finally LIN indicates that the x-axis should be linear. Another possibility is a logarithmic axis, which has not yet been implemented however. The parameters for the y-axis are given in the same way in the next 6 records.

The parameter NC specifies the number of curves to be plotted. For each curve a sub-block of 5 records has to be specified. The first parameter N indicates the number of points in the curve. If N is negative, no curve will be plotted; instead a marker will be plotted at the position of each data point. The parameter XMIN is the x-coordinate (range) of the first data point, whereas DX is the equidistant spacing. If DX had been specified as 0, then the N x-coordinates of the data points would be read from the plt file. In that case XMIN would be interpreted as an x-offset to be applied to the curve. The same rules apply to YMIN and DY . In the above example the y-values will therefore be read from the PLT file, and no y-offset will be applied. The offsets are mainly used for the stacked time series plots If both DX and DY are specified as 0, then mplot will first read all N x-values and then all y-values.