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# XmGrace day-to-day usage

Friday 8 July 2005

Before finding the wonderful XmGrace software, i’d loose time to do calculations, regressions, etc.

With this software, i’ve been able to do in a more robust manner and more rapidly everything i could do before and much more.

Here are some examples of what i’m using.

Some basics commands i use with XmGrace are detailed below.

### Renormalizing a plot (mostly angles between -180 and +180, you want it between 0 and 360 )

- Load your file into xmgrace
- Go to Data->Transformations->Evaluate expressions
- Select G0.S0
- Fill in the box with:

`y = y<=0 ? y + 360 : y`

It is a basic *if then else*: y equals the value resulting of the test y<=0. If the test is true then y = y+ 360 otherwise take the y value

### Subpopulation (for instance for an angle, where are the points above a certain value)

- Load your file into xmgrace
- Go to Data->Transformations->Sample points
- Select the desired set (presumably S0)
- Change sample type for ’Expression’
- Fill in the form ’Logical expression’ with your needs, for instance
`y=>50`

will select the population where all points are equal or above 50.

### Correlation between two states (for instance a sugar conformation and a dihedral angle)

- Load file1 into xmgrace (it will appear as set 0)
- Load file2 into xmgrace (it will appear as set 1)
- Go to Data->Transformations->Evaluate expressions
- Select g0.s1
- Fill in the box with:
`copy s1 to s2`

s2.x=s0.y - Accept
- Go back to the graph, hide s0 and s1, click on As (autoscale), you have your correlation :-) you can now fill in legends, etc.

### Getting informations about points (mean, std, max, min, ...)

- Load your file into xmgrace
- Go to Edit->Data sets
- Pick your set, the values will be displayed in the box below (rapid, isn’t it ?)

### Sending data through a pipe

`echo -e "1 2\n2 4\n3 6" |xmgrace -pipe`

### Sending data through a fifo

Create the fifo

`mkfifo fifo.pipe`

xmgrace -npipe fifo.pipe

Send the commands through the fifo

`echo "read \"data.out\"" > fifo.pipe`

echo autoscale > fifo.pipe

echo redraw > fifo.pipe

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