**Function:**
errorbar - plot with error bars

**Calling Sequences:**

**errorbar([x,y,er], options);
errorbar([x,y,erplus,erminus], options);**

**errorbar(L, options);**

**Parameters:**

**x,y, er, erplus, erminus - **
real numbers

**L **
- a set or list of error bar specifications, each in the form
**[x, y, er]**
or
**[x, y, erplus, erminus]**

**options**
- two-dimensional plot options, as well as
**horizontal**
and
** ticksize=**
size.

**Description:**

This creates a two-dimensional plot consisting of one or more error bars.

In the form
**errorbar([x,y,er])**
, the error bar extends from the point
**[x,y-er]**
to
**[x,y+er]**
. Thus this form is appropriate for a symmetrical data point
**y ± er**
.

In the form
**errorbar([x,y,erplus,erminus])**
, the error bar extends from
**[x,y+erminus]**
to
**[x,y+erplus]**
. Normally, one of
**erplus**
and
**erminus**
is positive and the other negative, but this is not checked.

If the option
**horizontal**
or
**horizontal=true**
is included, the error bar is horizontal instead of vertical, i.e. it extends from
**[x-er,y]**
to
**[x+er,y]**
or
**[x+erminus,y]**
to
**[x+erplus,y]**
.

Nothing is plotted at
**[x,y]**
itself, unless you include the
**symbol=**
option, which will plot a symbol at that point. Possible values are
**BOX**
,
**CROSS**
,
**CIRCLE**
,
**POINT**
and
**DIAMOND**
(but
**POINT**
is not very useful).

The
**ticksize=**
option specifies the length of the tick marks at the end of the error bars, in terms of the horizontal or vertical distance scale. Set this to 0 to have no tick marks. If this option is omitted, a default length will be used.

As in other plotting commands, the result of
**errorbar**
is a PLOT data structure. This can be assigned to a variable, saved in a file, etc.

This function is part of the Maple Advisor Database library, and must be loaded before use by the command
**readlib(errorbar);**
.

**Examples:**

`> `
**readlib(errorbar):**

`> `
**errorbar([seq([i,i^2,10/i],i=1..10)]);**

`> `
**errorbar([seq([i,i^2,-15/i,10/i],i=1..10)],symbol=circle,colour=red);**

`> `
**errorbar([seq([i,i^2,2/i],i=1..10)],symbol=diamond,horizontal,ticksize=5);**

**See also:**
__plot[options]__
,
__plot[structure]__

**Maple Advisor Database**
R. Israel, 1997