This post follows on from “Getting Started“.
In the lab we use IgorPRO for pretty much everything. We have many analysis routines that run in Igor, we have scripts for processing microscope metadata etc, and we use it for generating all figures for our papers. Even so, people in the lab engage with it to varying extents. The main battle is that the use of Excel is pretty ubiquitous.
I am currently working on getting more people in the lab started with using Igor. I’ve found that everyone is keen to learn. The approach so far has been workshops to go through the basics. This post accompanies the first workshop, which is coupled to the first few pages of the Manual. If you’re interested in using Igor read on… otherwise you can skip to the part where I explain why I don’t want people in the lab to use Excel.
IgorPro is very powerful and the learning curve is steep, but the investment is worth it.
These are some of the things that Igor can do: Publication-quality graphics, High-speed data display, Ability to handle large data sets, Curve-fitting, Fourier transforms, smoothing, statistics, and other data analysis, Waveform arithmetic, Matrix math, Image display and processing, Combination graphical and command-line user interface, Automation and data processing via a built-in programming environment, Extensibility through modules written in the C and C++ languages. You can even play games in it!
The basics
The first thing to learn is about the objects in the Igor environment and how they work.There are four basic objects that all Igor users will encounter straight away.
- Waves
- Graphs
- Tables
- Layouts
All data is stored as waveforms (or waves for short). Waves can be displayed in graphs or tables. Graphs and tables can be placed in a Layout. This is basically how you make a figure.
The next things to check out are the command window (which displays the history), the data browser and the procedure window.
Essential IgorPro
- Tables are not spreadsheets! Most important thing to understand. Tables are just a way of displaying a wave. They may look like a spreadsheet, but they are not.
- Igor is case insensitive.
- Spaces. Igor can handle spaces in names of objects, but IMO are best avoided.
- Igor is 0-based not 1-based
- Logical naming and logical thought – beginners struggle with this and it’s difficult to get this right when you are working on a project, but consistent naming of objects makes life easier.
- Programming versus not programming – you can get a long way without programming but at some point it will be necessary and it will save you a lot of time.
Pretty soon, you will go beyond the four basic objects and encounter other things. These include: Numeric and string variables, Data folders, Notebooks, Control panels, 3D plots – a.k.a. gizmo, Procedures.
Why don’t we use Excel?
- Excel can’t make high quality graphics for publication.
- We do that in Igor.
- So any effort in Excel is a waste of time.
- Excel is error-prone.
- Too easy for mistakes to be introduced.
- Not auditable. Tough/impossible to find mistakes.
- Igor has a history window that allows us to see what has happened.
- Most people don’t know how to use it properly.
- Not good for biological data – Transcription factor Oct4 gets converted to a date.
- Limited to 1048576 rows and 16384 columns.
- Related: useful link describing some spreadsheet crimes of data entry.
But we do use Excel a lot…
- Excel is useful for quick calculations and for preparing simple charts to show at lab meeting.
- Same way that Powerpoint is OK to do rough figures for lab meeting.
- But neither are publication-quality.
- We do use Excel for Tracking Tables, Databases(!) etc.
The transition is tough, but worth it
Writing formulae in Excel is straightforward, and the first thing you will find is that to achieve the same thing in Igor is more complicated. For example, working out the mean for each row in an array (a1:y20) in Excel would mean typing =AVERAGE(A1:y1) in cell z1 and copying this cell down to z20. Done. In Igor there are several ways to do this, which itself can be unnerving. One way is to use the Waves Average panel. You need to know how this works to get it to do what you want.
But before you turn back, thinking I’ll just do this in Excel and then import it… imagine you now want to subtract a baseline value from the data, scale it and then average. Imagine that your data are sampled at different intervals. How would you do that? Dealing with those simple cases in Excel is difficult-to-impossible. In Igor, it’s straightforward.
Resources for learning more Igor:
- Igor Help – fantastic resource containing the manual and more. Access via Help or by typing ShowHelpTopic “thing I want to search for”.
- Igor Manual – This PDF is available online or in Applications/Igor Pro/Manual. This used to be a distributed as a hard copy… it is now ~3000 pages.
- Guided Tour of IgorPro – this is a great way to start and will form the basis of the workshops.
- Demos – Igor comes packed with Demos for most things from simple to advanced applications.
- IgorExchange – Lots of code snippets and a forum to ask for advice or search for past answers.
- Igor Tips – I’ve honestly never used these, you can turn on tips in Igor which reveal help on mouse over.
- Igor mailing list – topics discussed here are pretty advanced.
- Introduction to IgorPRO from Payam Minoofar is good. A faster start to learning to program that reading the manual.
- Hands-on experience!
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Part of a series on the future of cell biology in quantitative terms.