Question: My code is the following, I would like a to assume iteratives values like '3' , '4' and so on. My code is like:

```
a=2
#perform some basic operation like:
b=a*2
#convert it to string
c=str(b)
p path1 u 1:($1<=0?$@c:1/0) w filledcurves y=0 

```

The solution proposed on similar topic here so far did not work.

Answer: 
You should use this syntax

```
  c=''.b

```

c will be equal to 'b'
If I correctly understand your minimal incomplete non-working example, I can only guess what you probably wanted to do, i.e. limit the plot of a dataset in a certain column which is selected by some variable. Correct? If my guess is true, I would do it the following way, no need for string conversion and the use of macros. Check `help column`.

```
a=2
# perform some basic operation like:
b=a*2
plot path1 u 1:($1<=0 ? column(b) : NaN) w filledcurves y=0 

```