# Understanding basic Plots behavior
**URL:** https://discourse.julialang.org/t/understanding-basic-plots-behavior/20479
**Category:** New to Julia
**Created:** [February 5, 2019, 4:56pm UTC](https://discourse.julialang.org/t/understanding-basic-plots-behavior/20479 "2019-02-05T16:56:41Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@tomf](https://discourse.julialang.org/u/tomf)
#### Post date: [February 5, 2019, 4:56pm UTC](https://discourse.julialang.org/t/understanding-basic-plots-behavior/20479/1 "2019-02-05T16:56:41Z")
I’m working my way through basic Julia exercises in a course. I have no problem with most of it but I haven’t yet grasped the odd way plots seem to work. Here’s a basic fn for calculating the steady state values of a logistic map:
```julia
function steady_state_values(r)
b = 0.25
for i in 1:400
b = r * b * (1-b)
end
attractor_values = zeros(150)
for i in 1:150
b = r * b * (1-b)
attractor_values[i] = b
end
return attractor_values
end
```
I want to vary the parameter r (along the x axis) and plot the corresponding steady state values along y. I’ve tried variations of this:
```julia
using Plots
first = true
for r = 2.9 : 0.001 : 4
y = steady_state_values(r)
x = fill(r, length(y))
if first
plot(x=x, y=y)
first = false
else
plot!(x=x, y=y)
end
end
```
Multiple calls to plot don’t seem to work–they result in no output-- so I plot the first array then call plot! subsequently. Even this doesn’t work. Can someone explain the logic? I come from matplotlib where you call figure() to begin, then any number of plotting operations, then show().
Plots.jl doesn’t seem to work that way. I’ve gone through a Plots.jl notebook but it didn’t clarify.
Thanks,
-Tom
---
### Author:  [@yha](https://discourse.julialang.org/u/yha)
#### Post date: [February 5, 2019, 5:25pm UTC](https://discourse.julialang.org/t/understanding-basic-plots-behavior/20479/2 "2019-02-05T17:25:35Z")
`plot(...)` creates and returns a plot object. `plot!(plt,...)` modifies the plot object `plt` and returns it. If `plt` is not specified, the last plot touched is used.
In Juno and Jupyter, a plot is shown when it’s the output of the cell/line that was just run. It’s just like with any return value, except instead of showing a textual representation, it’s graphical. Your code ended in a `for` loop, which has the value `nothing`, so nothing is shown or printed.
To see the plot, you can do
```julia
using Plots
plt = plot()
for r = ...
...
plot!(x, y) # or plot!(plt,x,y)
end
plt
```
The last line is to display the plot `plt`.
---
### Author:  [@jlperla](https://discourse.julialang.org/u/jlperla)
#### Post date: [February 5, 2019, 5:28pm UTC](https://discourse.julialang.org/t/understanding-basic-plots-behavior/20479/3 "2019-02-05T17:28:39Z")
Are you doing this in Jupyter or a `.jl` file? It can matter when `for` loops are involved… my suggestion is to stay in Jupyter for this sort of stuff unless your loops in a function.
---
### Author:  [@tomf](https://discourse.julialang.org/u/tomf)
#### Post date: [February 6, 2019, 2:52am UTC](https://discourse.julialang.org/t/understanding-basic-plots-behavior/20479/4 "2019-02-06T02:52:01Z")
I was doing this directly in Jupyter.
---
### Author:  [@tomf](https://discourse.julialang.org/u/tomf)
#### Post date: [February 6, 2019, 3:17am UTC](https://discourse.julialang.org/t/understanding-basic-plots-behavior/20479/5 "2019-02-06T03:17:30Z")
Thanks! That’s it exactly.
(In a Python notebook the plotting is a side effect, and the value doesn’t matter. Hence my confusion.)