Numerical calculation error using eval

I'm going through a calculation to convert RH to dewpoint, and for the first step I need to get the saturation vapor pressure, es.

es=eval(['6.11*exp(((Lv*Mw)/R)*((1/273)-(1./temp_ruc_',eventlist(z,:),')));']);

The error occurs within the exponent term...

I evaluated (Lv*Mw/R) and ((1/273)-(1./temp_ruc_',eventlist(z,:),')) separately, and both work.

I also tried the whole term using a sample temperature value (290 K), and I got the right answer:

((Lv*Mw)/R)*((1/273)-(1/290)) = 1.1632e+03

Given the range of temp values, all the answers should be in this range... But when I go through the calculation in full, as shown below, I get values ranging from -6 to +2...

eval(['((Lv*Mw)/R)*((1/273)-(1./temp_ruc_',eventlist(z,:),'))'])

What could be causing this error?

[Jan]

Avoid EVAL. It provokes errors and problems - obviously. And there is always a better solution.

Answer 1

[Walter Roberson]

http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F