-dvo: c -ambiguous command: c ( catalog cgrid clear create cursor ) -- -The shell is an interpretive programming language. -Variables are set as follows: - -
-dvo: $fred = 10 -- -Any expression within curly brackets {} is assumed -to be an arithmetical expression and is evaluated before the line is -executed. For example: - -
-echo {$fred*dcos(45)}
-
-
-would give the response 7.07107. There are math functions cos, sin,
-and tan, which operate on radian expressions, and also dcos, dsin,
-dtan, which operate on degree expressions. There are also the
-equivalent inverse functions: eg., asin and dasin return radians and
-degrees, respectively. The help section on Math defines all of the
-available math functions.
-
--! -- system call -? -- list commands -?? -- list variables -echo -- type this line -exec -- system call -exit -- exit program -help -- get help on a function -output -- redirect output to file -quit -- exit program -scan -- scan line from keyboard or file to variable -wait -- wait until return is typed -which -- show command -- -Most of these are self-explanatory. The command ?? prints the system -variables. The help command will provide help on a single -command or, without any arguments, will list all available help -files (this includes general help not associated with a specific -command). - -
-break -- escape from function -for -- loops -if -- logical cases -input -- read command lines from a file -macro -- deal with the macros -- -
-There are several options for programming in status. First, -a file which contains a series of commands can be executed with -input (filename). It is also possible to define macros which -will behave much like regular commands. A macro is defined by typing -macro name or macro create name followed by the -commands. Arguments to the macro are assigned to the variables $1 -.. $N and the number of arguments is given by $0. Macros may be -defined in input files, and in fact when status is -started, it loads the file ~/.statusrc which may contain -default macros. Simple loops and if statements can be performed, and -are quite useful for complex macros. - -
-'If' statements are similar in syntax to C if statements. Math -expresions in the if statement must be contained in curly braces, as -elsewhere. Variables with string values may use the logical == -operator to test if two strings are the same. 'For' loops are quite -simplistic. The form is: - -
-for var first last delta - (commands) -end -- -
-The value of $var will start at the value first and increment by -delta after each loop. The loop will stop after $var is greater -than stop. The value delta is optional, with 1 assumed. -The value of $var may be changed during the loop, and if set -beyong the value of last will end the loop early. - -
-box -- draw a box on the plot -clear -- erase plot -create -- create a new vector -cursor -- get coords from cursor -grid -- plot cartesian grid -hist -- create histogram from a vector -labels -- define labels for plot -limits -- define plot limits -plot -- plot a pair of vectors -print -- write vectors to file -ps -- define labels for plot -set -- vector math -style -- set the style for graph plots -vectors -- list vectors -zplot -- plot scaled points -- -
-In addition to scalar variables, status can manipulate and -display 1-D vector variables. Many of the commands which extract data -from the photometry database place the data in vectors as well as -plotting them. A vector can also be created based on a number -sequence with the command create name Nelements start delta. -The resulting vector has $Nelements$ entries, starting at a value of -$start$ and running until $start + delta*Nelements$. If $delta$ is -0.0, all elements will have the value of $start$. A histogram of a vector -may be made with the command hist, which creates a new vector -containing the histogram of the first vector. The data range and bin -size of the histogram are defined in same way as with create. This -makes it easy to create the index vector that goes with a histogram -vector: - -
-hist y Ny 1 100 0.1 -create dx 1 100 0.1 -- -
-The above will create a histogram of y in Ny and the index in dx. -Plotting this with plot dx Ny will show the histogram. - -
-Vector math is performed with a command of the form set new = - (expression). The expression is some math function employing - vectors and scalars. A complete listing of the math operators - available in set can be found in the help for set. - -
-Once vectors are defined, they may be plotted. A pair of vectors can -be plotted against each other if they have the same number of entries. -The plotting is performed on the graphics window, Kapa. There are -actually several graphics windows available to status, any of -which may be used to plot at any time. Some of the more complex -operations default to either graphics window 0 or 1, depending on the -context. Except for those functions with a pre-defined window, all -plotting functions apply to the current graphics window unless an -option -n N is given to specify a different window. The -plotting style is determined by the command style which can set -the line width, the line type (solid, dashed, dotted, etc), the point -type (box, cross, etc), the point size, the color, and whether a pair -of vectors is plotted as a sequence of points, a set of connected -lines, or a histogram. Some functions which make plots use their own -styles, as discussed below. The function limits lets the user -set the range of the plot axes, or check the current setting. The -command plot will plot a pair of vectors on the current graphics -window using the current plotting style for that window. The command -zplot will plot a pair of vectors with the point size scaled by -a third vector, with maximum and minimum point sizes representing -specified values. The cursor command goes the other way: this -command puts the Kapa window in cursor mode and waits for input from -Kapa. The user can then type any alphanumeric key on the graphics -windows and will be told both the pointer location (in the graphics -coordinates) and will have the coordinates stored in status -variables. For example, by typing ``1'' in the sky display window, -the RA and DEC of the pointer are stored in the variables $R1 -and $D1. This command can be used to let the user define -locations or regions of interest on the Kapa window. (Future addition: -button, which does the same with the mouse buttons).