# octavemagic: Octave inside IPython¶

In []:
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--- 0_old_cell
+++ 1_new_cell
@@ -0,0 +1 @@
+this is an added markdown cell


## Installation¶

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--- 1_old_cell
+++ 1_new_cell
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The octavemagic extension provides the ability to interact with Octave.  It depends on the oct2py package,
which may be installed using easy_install.
-
-To enable the extension, load it as follows:
+<!--split here, merge.py is smart enough to find that both cell have same ancestor-->

In []:
@@ diff for cell 5 @@
--- 1_old_cell
+++ 1_new_cell
@@ -1,4 +1,2 @@
-The octavemagic extension provides the ability to interact with Octave.  It depends on the oct2py package,
-which may be installed using easy_install.
-
+<!--split here, merge.py is smart enough to find that both cell have same ancestor-->
To enable the extension, load it as follows:

In [18]:
%load_ext octavemagic


## Overview¶

Loading the extension enables three magic functions: %octave, %octave_push, and %octave_pull.

The first is for executing one or more lines of Octave, while the latter allow moving variables between the Octave and Python workspace. Here you see an example of how to execute a single line of Octave, and how to transfer the generated value back to Python:

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--- 1_old_cell
+++ 1_new_cell
@@ -1,2 +1,3 @@
x = %octave [1 2; 3 4];
-x
+# here I change x to print x
+print x

In [20]:
a = [1, 2, 3]

%octave_push a
%octave a = a * 2;
%octave_pull a
a

Out[20]:
array([[2, 4, 6]])


When using the cell magic, %%octave (note the double %), multiple lines of Octave can be executed together. Unlike with the single cell magic, no value is returned, so we use the -i and -o flags to specify input and output variables.

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--- 2_old_cells
+++ 1_new_cell
@@ -1,3 +1,6 @@
%%octave -i x -o y
y = x + 3;
+# this should have been merge with the cell below
+# and this text added, the merge script is smart enough to detect that and only see
y


## Plotting¶

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--- 1_old_cell
+++ 1_new_cell
@@ -1,7 +1,8 @@
+#deleted cell above, no way to see it yet
%%octave -f svg

p = [12 -2.5 -8 -0.1 8];
x = 0:0.01:1;

polyout(p, 'x')
plot(x, polyval(p, x));


The plot size is adjusted using the -s flag:

In [24]:
%%octave -s 500,500

# butterworth filter, order 2, cutoff pi/2 radians
b = [0.292893218813452  0.585786437626905  0.292893218813452];
a = [1  0  0.171572875253810];
freqz(b, a, 32);

In [25]:
%%octave -s 600,200 -f png

subplot(121);
[x, y] = meshgrid(0:0.1:3);
r = sin(x - 0.5).^2 + cos(y - 0.5).^2;
surf(x, y, r);

subplot(122);
sombrero()


## Future work¶

After the next release of oct2py, we'll add the ability to interrupt/kill the current Octave session without restarting the Python kernel.