Interpolating Surface in R <p>I'm trying to interpolate a polynomial of the form</p> <p><code>z = Ax^2 + By^2 + Cxy + Dx + Ey + F</code></p> <p>In <code>R</code>, where the capital letters are constant coefficients.</p> <p>For the following data</p> <p>My horizontal axis is: <code>KSo&lt;-c(0.90,0.95,1.00,1.05,1.10)</code></p> <p>My vertical axis is: <code>T&lt;-c(1/12,3/12,6/12,1,2,5)</code></p> <p>And the data mapped by <code>KSo X T</code> are:</p> <p><code>14.2 13.0 12.0 13.1 14.5</code></p> <p><code>14.0 13.0 12.0 13.1 14.2</code></p> <p><code>14.1 13.3 12.5 13.4 14.3</code></p> <p><code>14.7 14.0 13.5 14.0 14.8</code></p> <p><code>15.0 14.4 14.0 14.5 15.1</code></p> <p><code>14.8 14.6 14.4 14.7 15.0</code></p> <p>In other words, the observed datum for <code>(1.00,6/12)</code> is <code>12.5</code></p> <p>How would I interpolate, for example, the predicted data for <code>(0.98,11/12)</code>? </p> <p>Edit: I found a nice package, <code>akima</code>, with the <code>bicubic</code> function, that uses splines. I'd still like to see what people suggest </p>