# Snippets (MATLAB)

This notebook contains snippets of code that are useful when working with MATLAB in IPython Notebooks.

## Displaying images from MATLAB¶

Passing variables into cells using the `%%matlab`

magic requires `h5py`

which is tricky to install. If you only need to pass in simple variables (strings) you can instead pass it in using Python string formatting and `mlab.run_code`

. Unfortunately, this means we don’t benefit from `pymatbridge`

automatically rendering figures. The class below is just a helper Python class to make it simpler to show the resulting figures from MATLAB commands.

```
import base64, os
os.environ['http_proxy'] = ''
class ImageOut(object):
def __init__(self, img):
with open(img) as f:
data = f.read()
self.image = base64.b64encode(data)
def _repr_png_(self):
return self.image
```

```
from pymatbridge import Matlab
mlab = Matlab()
mlab.start()
r = mlab.run_code('''
plot([1,2,3]);
''')
ImageOut( r['content']['figures'][0] )
```

## Pass widget variables into %%matlab magic¶

If you want to use widget controls in IPython notebooks you might find yourself wanting to pass those values into matlab cells using %%matlab magic. This snippet shows how you can use a callback function together with `interact`

to automatically update global vars, and then pass these into the matlab session using `-i`

.

*Note: you need hdf5 and h5py installed for this to work*

```
%load_ext pymatbridge
```

```
def widget_callback(**kwargs):
for k,v in kwargs.items():
globals()[k] = v
```

```
myvar=5
```

*Note: We define the variable first above, and pass the output var in as an default value. This means the widget wont reset if the cell is re-run, but will instead keep the current value. To reset the value just run the cell above.*

```
from IPython.html.widgets import interact
from IPython.html import widgets
i = interact(widget_callback,
myvar=widgets.IntSliderWidget(min=1, max=50, step=1, value=myvar, description="Reference spc:"),
)
```

```
%%matlab -i myvar
myvar
```

```
```

### Discussion

### Related posts

- Pathomx: Example Analysis
- Partial Least Squares Discriminant Analysis (PLS-DA)
- Getting Started with Pathomx
- Speed up MATLAB on MacOS X
- Gremlins in the Machine: Creating custom tools for the Pathomx data analysis platform

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