The purpose of this tutorial is to enable you to start making good quality scientific plots quickly. This will not cover everything - just some of the more important features.
When dealing with items in drop-down menus, we will use something of
the form
Things that are to be typed in will be presented in a typewriter font,
eg, type y = 3*sin(x)
.
xmgrace (data file)
This is most useful if you are in the same directory as the data file and the columns you want to graph are the first two. If you don't enter a data file name, xmgrace will start up with an empty plot.
The browser will show some of the files in your current directory (the ones that are selected using the filter). Select the file you want and double click or hit return or click OK to bring it into the program. You should see a black curve drawn on a graph.
When selecting the file, choose "Block data" from the "Load as" menu. If the read was successful, a window should pop up asking you to create a set from the block data. At the top it will list how many columns of data were read. First choose the type of set you would like. Choose the columns for the x- and y- coordinates using the drop down menus. The values Y1 through Y4 are used for selecting error bars as may be needed by other set types.
This lists all the datasets, and for the selected set, its type and a few statistics. To eliminate a set from the plot, select it and then press the right mouse button. A menu should appear from which you can select kill or kill data. The former totally eliminates everything associated with a set while the latter eliminates the data but keeps the settings for it so that if new data is read into the set, it will have the same properties like colouring and line width, etc.
Aspects of the axes are controlled by the axes popup. To see the effect of a change, you have to hit the "Apply" button. In the Main menu:
This allows you to change the way the sets are graphed. Practically all aspects of the curves are configurable including colour, line thickness, symbols, drop lines, fills, etc. When the window pops up, there will be a list of the sets with their number (eg. G0.S1 refers to set 1 in graph 0). To see the effect of a change, you have to hit the "Apply" button. In the Main menu:
We can now fill in the title of the graph and by clicking on the "Titles" tab, the font and size and colour can be chosen.
Using evaluate expression allows you to create a set by applying an explicit formula to another set. All the classical mathematical functions are available (cos, sin, etc., but also more complex ones). All trigonometric functions use radians by default but you can specify a unit if you prefer to say cos (x rad) or sin (3 * y deg). For the full list of available numerical functions and operators, see Operators and functions.
In the formula, you can use X, Y, Y1, ..., Y4 to denote any coordinate you like from the source set. An implicit loop will be used around your formula so if you say:
x = x - 4966.5
you will shift all points of your set 4966.5 units to the left.
You can use more than one set in the same formula, like this:
y = y - 0.653 * sin (x deg) + s2.y
which means you use both X and Y from the source set but also the Y coordinate of set 2. Beware that the loop is a simple loop over the indices, all the sets you use in such an hybrid expression should therefore have the same number of points and point i of one set should really be related to point i of the other set. If your sets do not follow these requirements, you should first homogenize them using interpolation.
This saves the current plot parameters into a file so that you can produce the exact same graph without starting from scratch. If the current graph has not been saved already, you will be prompted for a name.
This saves the current plot parameters into a file - you will be prompted for a name.
This opens and graphs an earlier plot using the previously saved parameters.
This prepares to either print the graph on the printer, or produce a file for viewing.
This executes your wishes from the "Print setup" menu, printing to the printer using a Unix command or producing a file.
Along the left-hand side of the canvas (if shown) is the ToolBar. It is armed with several buttons to provide quick and easy access to the more commonly used Grace functions.
Draw
: This will redraw the canvas and sets.
Useful if "Auto Redraw" has been deselected in the Edit/Preferences
dialog or after executing commands directly from the Window/Commands
interpreter.
Lens
: A zoom lens. Click on the lens, then select the
area of interest on the graph with the "rubber band". The region
enclosed by the rubber band will fill the entire graph.
AS
: AutoScale. Autoscales the graph to contain all
data points of all visible (not hidden) sets.
Z/z
: Zoom in/out by 5%. The zoom percentage can be
set in the Edit/Preferences dialog.
Arrows
: Scroll active graph by 5% in the arrow's
direction. The scroll percentage can be set in the
Edit/Preferences dialog.
AutoT
: AutoTick Axes. This will find the optimum
number of major and minor tick marks for both axes.
AutoO
: Autoscale On set. Click the AutoO
button, then click on the graph near the set you wish to use for
determining the autoscale boundaries of the graph.
ZX,ZY
: Zoom along an axis. These buttons work like the
zoom lens above but are restricted to a single axis. AX,AY
: Autoscale the limits on one axis only.
The following buttons deal with the graph stack and there is a good example under Help/Examples/General Intro/World Stack.
Pu/Po
: Push and pop the current world settings to/from
the graph stack. When popping, makes the new stack top current.PZ
: Push before Zooming. Functions as the zoom lens,
but first pushes the current world settings to the stack. Cy
: Cycles through the stack settings of the active
graph. Each graph may have up to twenty layers on the stack.
Exit
: ...Arguments of both operators and functions can be either scalars or vector arrays. Arithmetic, logical, and comparison operators are given in tables below.
Operator | Description |
+ | addition |
- | substraction |
* | multiplication |
/ | division |
% | modulus |
^ | raising to power |
Operator | Description |
AND or && | logical AND |
OR or || | logical OR |
NOT or ! | logical NOT |
Operator | Description |
EQ or == | equal |
NE or != | not equal |
LT or < | less than |
LE or <= | less than or equal |
GT or > | greater than |
GE or >= | greater than or equal |
Another conditional operator is the "?:" (or ternary) operator, which operates as in C and many other languages.
(expr1) ? (expr2) : (expr3);
This expression evaluates to expr2 if expr1 evaluates to TRUE, and expr3 if expr1 evaluates to FALSE.
Function | Description |
abs(x) | absolute value |
acos(x) | arccosine |
acosh(x) | hyperbolic arccosine |
asin(x) | arcsine |
asinh(x) | hyperbolic arcsine |
atan(x) | arctangent |
atan2(y,x) | arc tangent of two variables |
atanh(x) | hyperbolic arctangent |
ceil(x) | greatest integer function |
cos(x) | cosine |
cosh(x) | hyperbolic cosine |
exp(x) | e^x |
fac(n) | factorial function, n! |
floor(x) | least integer function |
irand(n) | random integer less than n |
ln(x) | natural log |
log10(x) | log base 10 |
log2(x) | base 2 logarithm of x |
maxof(x,y) | returns greater of x and y |
mesh(n) | mesh array (0 ... n - 1) |
mesh(x1, x2, n) | mesh array of n equally spaced points between x1 and x2 inclusive |
minof(x,y) | returns lesser of x and y |
mod(x,y) | mod function (also x % y) |
pi | the PI constant |
rand | pseudo random number distributed uniformly on (0.0,1.0) |
rand(n) | array of n random numbers |
rint(x) | round to closest integer |
rsum(x) | running sum of x |
sin(x) | sine function |
sinh(x) | hyperbolic sine |
sqr(x) | x^2 |
sqrt(x) | x^0.5 |
tan(x) | tangent function |
tanh(x) | hyperbolic tangent |
Function | Description |
chdtr(df, x) | chi-square distribution |
chdtrc(v, x) | complemented Chi-square distribution |
chdtri(df, y) | inverse of complemented Chi-square distribution |
erf(x) | error function |
erfc(x) | complement of error function |
fdtr(df1, df2, x) | F distribution function |
fdtrc(x) | complemented F distribution |
fdtri(x) | inverse of complemented F distribution |
gdtr(a, b, x) | gamma distribution function |
gdtrc(a, b, x) | complemented gamma distribution function |
ndtr(x) | Normal distribution function |
ndtri(x) | inverse of Normal distribution function |
norm(x) | gaussian density function |
pdtr(k, m) | Poisson distribution |
pdtrc(k, m) | complemented Poisson distribution |
pdtri(k, y) | inverse Poisson distribution |
rnorm(xbar,s) | pseudo random number distributed N(xbar,s) |
stdtr(k, t) | Student's t distribution |
stdtri(k, p) | functional inverse of Student's t distribution |
Function | Description |
MIN(x) | min value of array x |
MAX(x) | max value of array x |
AVG(x) | average of array x |
SD(x) | standard deviation of array x |
SUM(x) | sum of all elements of array x |
INT(x,y) | integral of y dx |
IMIN(x) | index of min value of array x |
IMAX(x) | index of max value of array x |