## Bar-n

In GNU Plot, if you want the figure has the labelled axis, you can always use
the `set xlabel`

or `set ylabel`

command. However, if you want to have the label
more fancy, you need to consult the
ps_guide.ps and
then to see which fancy symbols you want to use. So far, `postscript enhanced`

terminal is the only flexible terminal for plotting.

In the ps_guide, it said `@`

means to align the superscripts and subscripts,
however, it is wrong! The `@`

symbol actually means to place the next symbol (or
block of symbols) without allocating spaces. Hence the forthcoming symbols will
occupy the same place with this one. Take bar-n (i.e. \(\bar{n}\)) as an example,
the “bar” bears the code 305 (octal) in Times font, so this command will put
bar-n as the y-axis label:

```
set ylabel {/Times-Roman @{\305\305}n}
```

I need two 305 because the bar is rather short, so I need two to cover the whole n.

## Polar polt

Easy, issue these commands first:

```
set polar
set grid polar
set angle radians
```

then use `t`

as the radian angle and plot for r(t)

## Argand Diagram

Plotting complex numbers in the form of argant diagram can be done in the
following way. Firstly, declare parametric plot (`set parametric`

). Secondly,
define a complex function. The imaginary number is written as `{0,1}`

. Thirdly,
plot the complex function by obtaining argument and magnitude via arg() and
abs() functions. The following is an example for plotting
\(g(\omega)=\frac{k}{j\omega(-\omega^2+j\omega+4)}\) with different values of \(k\),

```
unset border
set angles radians
unset key
set parametric
set samples 50000, 50000
set xzeroaxis
set yzeroaxis
set xtics axis
set ytics axis
g(w,k)=k/(w*{0,1}*(-w**2+w*{0,1}+4))
paramx(t,k)=abs(g(t,k))*cos(arg(g(t,k)))
paramy(t,k)=abs(g(t,k))*sin(arg(g(t,k)))
plot [t=0:1000] [-1.5:0.5] [-1.5:0.5] \
paramx(t,1),paramy(t,1) , \
paramx(t,3),paramy(t,3) , \
paramx(t,3.5),paramy(t,3.5) , \
paramx(t,4),paramy(t,4)
```