how can I express this equation in gnuplot?

In gnuplot, how would I express something like this:

To express inequality, we'll use the ternary operator, where (in pseudocode)

```if CONDITION:
DO_A
else:
DO_B
```

is expressed as

```CONDITION ? DO_A : DO_B
```

so in our case,

```if a != x:
f(x) = (a - x)**(0.04)
else:
f(x) = 0
```

is expressed as

```f(x,a) = (a != x) ? (a - x)**(0.04) : 0
```

Note that we are expressing the 25th-root, or n^(1/25), as n^(0.04).

Plotting this equation will look something like the following:

```reset
f(x,y) = (y != x) ? (y - x)**(0.04) : 0
unset colorbox
set isosample 300, 300
set xlabel 'x'
set ylabel 'y'
set title '(y - x)^{0.04} != 0'
set sample 300
set pm3d map
splot [-500:500] [-500:500] f(x,y)
```

which yields

Another way to express this is to simply do

```reset
f(x,y) = (y - x)**(0.04) != 0
unset colorbox
set isosample 300, 300
set xlabel 'x'
set ylabel 'y'
set title '(y - x)^{0.04} != 0'
set sample 300
set pm3d map
splot [-500:500] [-500:500] f(x,y)
```

which yields

In this second image, Gnuplot is plotting the imaginary part of the equation (i.e., when x > a).