Trigonometry function in Igor
Igor_user
Fri, 03/12/2010 - 06:27 am
I am using Igor to convert a wave from one factor to another using a sine function.
Igor can regonise e.g sin(pi/180) directly, but when I try to input the inverse of sin with sin^-1(pi/180), it doesn't work for this command.
Does anyone know how to input a function which includes a term for an inverse trigonometric function?
Many thanks!
John Weeks
WaveMetrics, Inc.
support@wavemetrics.com
March 12, 2010 at 09:30 am - Permalink
Problems,
The sine function is this
'Lamda'=2*'d'*sin('theta')
I have two Lamdas, 'Lamda_1' = 0.826026 & 'Lamda_2' =1.542515
and I have an original wave '2theta_1' which is 2*'theta_1' and is worked out in 'Lamda_1'.
Now, I want to convert the '2theta' into '2theta_2' which is worked out with 'Lamda_2'.
So, what i did was to rearrange the equation for '2theta_1' and get a set of values for 'd'.
'd_space' = 0.826026/2/sin('2theta_1'/2)
And then use this with 'Lamda_2' to get a new set of data for '2theta_2'.
'2theta_2' = 2*asin(1.542515/2/'d_space')
AppendToTable '2theta_2'
But then, what it appears is only a column header named with '2theta_2'. No data was actually displayed for this wave.
I tried to plot a graph using '2theta_2'. But what it comes out is not correct.
Can anyone tell if this is a command error?
March 13, 2010 at 03:12 am - Permalink
If d_space contains zeros then 1.542515/2/'d_space' will be INF and asin(1.542515/2/'d_space') will be NaN (not-a-number which is displayed in a table as a blank cell.
March 13, 2010 at 01:35 pm - Permalink
I looked through the entire wave of 'd_space', some of the numbers are -ve and some are +ve, but none of them is zero.
In fact, the mathematics that I applied is correct, so it shouldn't come out with something which doesn't look like what it's supposed to be.
Anyway, is there an alternative way to get '2theta_2' in terms of the 'lambda_2'?
March 14, 2010 at 01:09 am - Permalink
the sin-functions returns the sine of an angle in radians, your XRD(?) pattern will be in degrees.
Would this work?
wave TwoTheta
variable lambda1 = 0.82
variable lambda2 = 1.54
Duplicate/O TwoTheta d_spacing, newTwoTheta
d_spacing = lambda1/ (2* sin( (TwoTheta*pi/180)/2 ) )
newTwoTheta = asin( lambda2 / (2*d_spacing) ) * 180/pi
Killwaves/Z d_spacing
end
Christian
March 15, 2010 at 09:49 am - Permalink