Extracting temperature data from netCDF file and then trying to take time derivative of temperature

I am trying to extract temperature data from a netCDF file:

SATh = ncread('spatially_int_Historical.nc','A_sat');
SATFAST = ncread('spatially_int_1000GT_FAST.nc','A_sat');

Then I want to calculate the temperature anomaly (w.r.t. the first i value, year 1800):

for i=1,200
    SATdiffhist(i) = SATh(i) - SATh(1);
i = i+1
end

for i=1,1000
    SATdiffFAST(i) = SATFAST(i) - SATh(1);
i = i+1
end

Finally, the goal is to calculate the time derivative of the temperature anomaly:

deltaSATdiffFAST(1) = SATdiffFAST(1) - SATdiffhist(200);
for i=2,1000
    deltaSATdiffFAST(i) = SATdiffFAST(i) - SATdiffFAST(i-1)
i = i+1
end

deltaSATdiffVFAST(1) = SATdiffVFAST(1) - SATdiffhist(200);
for i=2,1000
    deltaSATdiffVFAST(i) = SATdiffVFAST(i) - SATdiffVFAST(i-1);
i = i+1
end

The problem seems to arise from the fact that the original temperature data (SATh and SATFAST) are not referenced to an i-value, so the for loops only iterate once.

Is there a way to rectify this?

Answer 1

[per isakson]

    for i=1,200
        SATdiffhist(i) = SATh(i) - SATh(1);
    i = i+1
    end

with Matlab syntax

    for i=1:200
        SATdiffhist(i) = SATh(i) - SATh(1);
    end

However,

    SATdiffhist = SATh - SATh(1);

is faster