# Drawing a curve, given points and slope values in said points

``````x     y     dy/dx
...
... input data
...
``````

Given input points (x, y values), a variety of curves can be drawn through them depending on boundary conditions (starting tangent, end tangent) and interpolation used.

Now, I have a set of points (x, y values) but also (dy/dx... slope values) as input data. What software would enable me to draw a curve taking into account slope values?

• It's not clear what you're asking, but I'll take a guess. You want to graph a series of data points with the additional constraint that the local slope at each data point is specified by a set of dy/dx values. And you're asking what software could do that for you. Is that right? If that's true, I'd suggest this is more of a computational issue than a software issue. Con'd... – Bandersnatch Dec 22 '17 at 14:30
• I doubt there's a software solution, but you can calculate a new data set that accomplishes what you want to do. First, create a new column of x-data values, adding a new point on either side of your existing x-values, with each new point being say 10% of the distance to the next point. e.g. If you have x values at 0,10 and 20, add new ones at 1,9,11,19 and 21. Next, calculate y-values for each new x-value using the dy/dx value. Finally, graph the new data. You might use a "Smooth Lined Scatter" graph to have Excel smooth out any large "kinks", or just a Lined Scatter to clearly see any such – Bandersnatch Dec 22 '17 at 14:46
• Note: all of the above data synthesis can be accomplished fairly easily with formulas in Excel. – Bandersnatch Dec 22 '17 at 14:47