I am trying to model mechanical response under constraint in materials, and I know that I need this kind of function if I want my model to be accurate. 
The point is, I have absolutely no idea about how to build such function (equal to 0 if x>R), and I don't really want to use B-splines or I don't know what interpolation or something. I already tried this function : $$\frac{e^{\frac{-x}{2}}\times sin(2\pi x/R)\times (R-x)}{x^2}$$ but it just doesn't work. I know that I can put E in my sin, but then it causes another problem...
So, if anybody has an idea, even something that isn't exactly looking like this plot, or if you know some encyclopedia where I can find a typical function data-base or something, feel free to help me :)