How to do differentiation in Matlab

clc;
clear;
THT = 0:12:360;
L_spm = [67.14387343 67.08087868 71.27139857 77.8011002	83.48598354	86.53313448	86.96218524	86.54264509	86.55222711	86.96002063	86.43128473	83.48041917	77.77271123	71.24225453	67.07111986	67.25745156	67.08157624	71.23009025	77.76475253	83.46615144	86.42639244	86.96777069	86.54247287	86.56340306	86.9412182	86.52945688	83.49766473	77.78259172	71.25635182	67.06788196	67.14602485];

How to differentiate L_spm with respect to THT? Thanks.

Answer 1

[James Tursa]

Are you just asking for piecewise linear differencing for derivative calculations between the points? E.g.,

THT = 0:12:360;
L_spm = [67.14387343 67.08087868 71.27139857 77.8011002	83.48598354	86.53313448	86.96218524	86.54264509	86.55222711	86.96002063	86.43128473	83.48041917	77.77271123	71.24225453	67.07111986	67.25745156	67.08157624	71.23009025	77.76475253	83.46615144	86.42639244	86.96777069	86.54247287	86.56340306	86.9412182	86.52945688	83.49766473	77.78259172	71.25635182	67.06788196	67.14602485];
d = diff(L_spm) ./ diff(THT)

d = 1x30

-0.0052 0.3492 0.5441 0.4737 0.2539 0.0358 -0.0350 0.0008 0.0340 -0.0441 -0.2459 -0.4756 -0.5442 -0.3476 0.0155 -0.0147 0.3457 0.5446 0.4751 0.2467 0.0451 -0.0354 0.0017 0.0315 -0.0343 -0.2526 -0.4763 -0.5439 -0.3490 0.0065

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Or are you asking how to curve fit and calculate derivatives from the curve?

[Anurag Sharma]

Thanks for your response & helping me with the differentiation. How do I plot d = diff(L_spm) ./ diff(THT).

When I am plotting 'd' with resepct to 'THT' using "plot(THT,d)". It gives me following error "Error using plot Vectors must be the same length"

[Torsten]

THT = 0:12:360;
L_spm = [67.14387343 67.08087868 71.27139857 77.8011002	83.48598354	86.53313448	86.96218524	86.54264509	86.55222711	86.96002063	86.43128473	83.48041917	77.77271123	71.24225453	67.07111986	67.25745156	67.08157624	71.23009025	77.76475253	83.46615144	86.42639244	86.96777069	86.54247287	86.56340306	86.9412182	86.52945688	83.49766473	77.78259172	71.25635182	67.06788196	67.14602485];
d = gradient(L_spm)./gradient(THT);
plot(THT,d)