C2_W2_Backprop Optional Lab - Week 2

Why does this command (dJ_dw.subs([(sd,d),(sx,x)])) NOT substitute for the value of ‘d’ which is calculated in one of the previous cells?

Prior to running this line, we arrived at dJ_dw = (d)(x).

Now we run the line dJ_dw.subs([(sd,d),(sx,x)]) to substitute the values of d and x in the derivative. Only x seems to be substituted as the output received is ‘2d’. Please clarify. Thanks

The command substitutes d for sd. I think the explanation is that, if you print sd, it no longer represents the symbol for d because it has been overwritten by a - y. Therefore, it does not replaces the symbol d with the value of d.


Thanks for the response. I tested that theory and it works. I defined a function whose derivative had two variables with direct assignments to integers. Subs was able to substitute both the variables with its integer values.

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Hey @Macwin_Savio_Dsouza, thank you for letting us know. :slight_smile: