I have been trying to find an analytical expression for the following: $\frac{\partial {X^{+}}}{\partial {X}}$ In my case, $X$ has a constant rank. I've found the formula for differentiating a pseudoinverse in [Goulob's paper](http://i.stanford.edu/pub/cstr/reports/cs/tr/72/261/CS-TR-72-261.pdf) (equation 4.12): $$ \frac{\mathrm d}{\mathrm d x} A^+(x) = -A^+ \left( \frac{\mathrm d}{\mathrm d x} A \right) A^+ +A^+ A{^+}^T \left( \frac{\mathrm d}{\mathrm d x} A^T \right) (1-A A^+) + (1-A^+ A) \left( \frac{\mathrm d}{\mathrm d x} A^T \right) A{^+}^T A^+ $$ but I can't see how to input the original matrix. I've tried $$ \frac{\mathrm d}{\mathrm d A} A^+(A) = -A^+ \left( \frac{\mathrm d}{\mathrm d A} A \right) A^+ +A^+ A{^+}^T \left( \frac{\mathrm d}{\mathrm d A} A^T \right) (1-A A^+) + (1-A^+ A) \left( \frac{\mathrm d}{\mathrm d A} A^T \right) A{^+}^T A^+ $$ but it doesn't seem to give the right answers. What should $\frac{\mathrm d A^T}{\mathrm d A}$ and $\frac{\mathrm d A}{\mathrm d A}$ evaluate to?