I am running an idealized experiment with a atmospheric model with output in the format of netcdf. But the netcdf file header does not describe the variable and and dimension clearly. for example :
netcdf qc3d {
dimensions:
Time = UNLIMITED ; // (1453 currently)
bottom_top = 45 ;
south_north = 32 ;
west_east = 12288 ;
variables:
float Time(Time) ;
Time:axis = "Time" ;
Time:long_name = "Time" ;
Time:standard_name = "Time" ;
Time:units = "minutes since 1900-01-01 " ;
double zc(bottom_top) ;
zc:axis = "Z" ;
zc:long_name = "vertical height of model layers, MSL" ;
zc:standard_name = "altitude" ;
zc:units = "m" ;
zc:positive = "up" ;
double yc(south_north) ;
yc:axis = "Y" ;
yc:long_name = "y-coordinate of grid cell centers in Cartesian system" ;
yc:units = "m" ;
double xc(west_east) ;
xc:axis = "X" ;
xc:long_name = "x-coordinate of grid cell centers in Cartesian system" ;
xc:units = "m" ;
float qc(Time, bottom_top, south_north, west_east) ;
qc:long_name = "cloud water mixing ratio" ;
qc:standard_name = "cloud_water_mixing" ;
qc:units = "kg kg-1" ;
qc:_FillValue = 9.96921e+36f ;
qc:missing_value = 9.96921e+36f ;
// global attributes:
:model_tag = "CSU VVM" ;
:references = "http://kiwi.atmos.colostate.edu/pubs/joon-hee-tech_report.pdf" ;
:contact = "jung#atmos.colostate.edu" ;
:institution = "Colorado State University" ;
:VVM_casename = "GATE_PHASE_III " ;
}
there are 4 dimensions, Time(Time), zc(bottom_top), yc(south_north), xc(west_east) and 5 variable in which first 4 variables should be the dimension of the fifth variable, so called qc. But it seems not. The dimension is just a series number index from 1 to 45, 32 ...whatever else.
I would like to calculate some variable which is the function of pressure. in the CDO the script is like this
cdo expr,"pottemp=temp*((100000/clev(temp))^0.287);" ifile pottemp.nc
(this code is from here)
but I just obtain a series of index like 1 ,2 ,3 ... not the real pressure level when I use this function, clev(qv).
So how can I rewrite the variable dimension like qc from
qc(Time, bottom_top, south_north, west_east) ;
to
qc(Time, zc, yc, xc) ;
I think it's possible for me to finish this in matlab, but I just don't want to open this dataset because it's size is too large... so I am trying to find some tools like ncks or cdo, but still failed to do this.
thanks a lot.
With NCO try
ncap2 -s 'pottemp=temp*((100000/zc)^0.287)' in.nc out.nc
ncap2 documentation
extending answer to cover additional question below:
first use ncap2 to explicitly set zc to the values in the ascii file:
ncap2 -s 'zc[$zc]={1.5,900,2500,3500}' in.nc out.nc
(assuming zc is size 4 dimension). then define pottemp based on that zc.
Related
I have a multi-fuction script that is supposed to ask the user for 4 different cars and weigh them based on ratings to give the user the best car to purchase.
What I want to do is have a prompt for every car the user inputs so the user can put in data for each variable the user decides to use. However, when titling the prompt I want to use the cars name in the prompt. It seems impossible to me and Im not sure what to do, im very new to coding.
Main Script
prompt1 = {'How Many Cars (4): '};
title1 = 'Cars';
answer1 = inputdlg(prompt1, title1, [1 40]);
Q1 = str2double(answer1{1});
[N] = Group_Function1(Q1);
Car1 = N(1); %Stores the names of the cars
Car2 = N(2);
Car3 = N(3);
Car4 = N(4);
prompt2 = {'How Many Variables (4): '};
title2 = 'Variables';
answer2 = inputdlg(prompt2, title2, [1 50]);
fprintf('This code can accept costs between 0-100000\n');
fprintf('This code can accept top speeds between 0-200\n');
fprintf('This code can also accept the terms none, some, & alot\n');
fprintf('This code can accept safety ratings between 0-5\n');
Q2 = str2double(answer2{1});
[V,W] = Group_Function2(Q2);
W1 = W(1); %Stores the weights of the varibles
W2 = W(2);
W3 = W(3);
W4 = W(4);
for h=1:Q1
[H] = Group_Function3(V);
Weights(h,:)=H;
end
Group_Function1
function [N] = Group_Function1(Q1)
for Q = 1:Q1
prompt = {'Name of Car:'};
title = 'Car Name';
answer = inputdlg(prompt,title, [1 80])';
N(Q) = answer(1);
end
Group_Function2
function [V,W] = Group_Function2(Q2)
for Q=1:Q2
prompt = {'Variable? (Negative Variables First):','weights in decimal
form?'};
title = 'Variables and Weights';
answer = inputdlg(prompt,title, [1 80])';
V(Q)=answer(1);
W(Q)=str2double(answer{2});
s=sum(W);
end
if s~=1
fprintf('Weights do not add up to 1. Try Again!\n');
Group_Function2(Q2);
end
end
Group_Function3 (Where the problem occurs)
function [H] = Group_Function3(V)
prompt = {V};
title = ['Variable Ratings For' Group_Function1(answer{1})];
h = inputdlg(prompt, title, [1 80])';
end
The Problem
For 'Group_Function3' I want the prompt to include the users inputs from 'Group_Function1' so that when the prompt comes up to input the answers I know which vehicle I am entering for.
Each function runs in its own workspace, it means it does not know the state or content of variables outside of it. If you want a function to know something specific (like the name of a car), you have to give that to the function in the input parameters. A function can have several inputs parameters, you are not limited to only one.
Before going into the Group_Function3 , I'd like to propose a new way for Group_Function1.
Group_Function1 :
You run a loop to ask independantly for each car name. It is rather tedious to have to validate each dialog boxe. Here is a way to ask for the 4 car names in one go:
replace the beginning of your script with:
title1 = 'Cars';
prompt1 = {'How Many Cars (4): '};
answer1 = inputdlg(prompt1, title1 );
nCars = str2double( answer1{1} );
CarNames = getCarNames(nCars) ; % <= use this function
% [N] = Group_Function1(Q1); % instead of this one
and replace Group_Function1 with:
function CarNames = getCarNames(nCars)
title = 'Car Names';
prompt = cellstr( [repmat('Name of car #',nCars,1) , sprintf('%d',(1:nCars)).'] ) ;
CarNames = inputdlg( prompt, title, [1 80] ) ;
end
Now CarNames is a cell array containing the name of your 4 cars (as your variable N was doing earlier. I recommend sligthly more explicit variable names).
You can run the rest of your code as is (just replace N with CarNames, and Q1 with nCars).
Group_Function3 :
when you get to the Group_Function3, you have to send the current car name to the function (so it can use the name in the title or prompt). So replace your Group_Function3 as following (we add an input variable to the function definition):
function H = Group_Function3( V , thisCarName )
prompt = {V};
title = ['Variable Ratings For' thisCarName];
H = inputdlg(prompt, title, [1 80])';
end
and in your main script, call it that way:
for h = 1:nCars
thisCarName = carNames{h} ;
H = Group_Function3( V , thisCarName ) ;
% ...
% anything else you want to do in this loop
end
I have a global data at 0.25 degree resolution that I'd like to mask so that it only contains data values over land.
The data covers full 360 degrees in the lon dimension and from -60 to 60 degrees in the lat dimension.
The file header, as well as summary lat and lon coordinate values, are listed below:
netcdf cmorph_global_daily {
dimensions:
lat = UNLIMITED ; // (480 currently)
lon = 1440 ;
time = 7305 ;
variables:
float lat(lat) ;
lat:units = "degrees_north" ;
lat:long_name = "Latitude" ;
float lon(lon) ;
lon:units = "degrees_east" ;
lon:long_name = "Longitude" ;
float prcp(lat, lon, time) ;
prcp:_FillValue = NaNf ;
prcp:units = "mm" ;
prcp:standard_name = "precipitation" ;
prcp:long_name = "Precipitation" ;
prcp:description = "CMORPH Version 1.0BETA Version, daily precip from 00Z-24Z" ;
int time(time) ;
time:units = "days since 1900-01-01" ;
time:long_name = "Time" ;
time:calendar = "gregorian" ;
// global attributes:
:history = "Mon Mar 26 10:44:42 2018: ncpdq -a lat,lon,time cmorph_adjusted_daily.nc latlontime/cmorph_adjusted_daily.nc\nThu Mar 15 10:21:10 2018: ncks -4 cmorph_adjusted_daily.nc cmorph_adjusted_daily.nc" ;
:nco_openmp_thread_number = 1 ;
:title = "CMORPH Version 1.0BETA Version, daily precip from 00Z-24Z" ;
:NCO = "4.7.2" ;
data:
lat = -59.875, -59.625, -59.375, -59.125, ..., 59.125, 59.375, 59.625, 59.875 ;
lon = 0.125, 0.375, 0.625, 0.875, 1.125, ..., 359.125, 359.375, 359.625, 359.875 ;
I would prefer to do this using Python/numpy and/or NCO since that's my typical toolset.
Once you have a variable on the same grid to mask with, you can use
ncap2 where, e.g.,
ncap2 -s 'where(LANDMASK != 1) prcp=prcp#_FillValue' in.nc out.nc
If your mask is on a different grid than your data, you can use
(on Linux/Mac) the masking features of ncremap, e.g., to remap your data to your mask (or visa versa) with something like
ncremap --msk_dst=LANDMASK -d mask.nc prcp_in.nc prcp_out.nc
A solution with CDO
# make landseamask on 0.25 grid with 1 for land and missing for sea
cdo -P 8 -f nc2 setctomiss,0 -gtc,0 -remapcon,r1440x720 -topo seamask.nc
# not sure if you need to do this but lets put your data on same grid
cdo remapcon,r1440x720 yourdata.nc yourdataremap.nc
# now mask the data
cdo mul yourdataremap.nc seamask.nc yourdatamasked.nc
hope that works...
EDIT: You can also simply make the landsea mask directly on the grid of your data in this way:
# make landseamask on 0.25 grid with 1 for land and missing for sea
cdo -P 8 -f nc setctomiss,0 -gtc,0 -remapcon,yourdata.nc -topo seamask.nc
# now mask the data
cdo mul yourdataremap.nc seamask.nc yourdatamasked.nc
I don't know why but I am getting this error:
Error in mr_lsbpex (line 3)
dlen = uint32(0) ;
Output argument "a" (and maybe others) not assigned during call to "E:\path\mr_lsbpex.m>mr_lsbpex"
I have tested "dlen = uint32(0) ;" in matlab enviorment (outside of this function) and everything was OK. Here is my code:
function a = mr_lsbpex ( r, p )
% extract from an array
dlen = uint32(0) ;
s = size (r) ;
rnd = rand (s(1),s(2)) ;
rd = 32 ;
rl = s(2) ;
for i=1:s(2)
if rnd(1,i)<rd/rl
d = bitget (round(r(1,i)/p),1);
dlen = bitset (dlen,rd,d);
rd = rd -1 ;
end
rl = rl -1 ;
end
if (dlen > 10000000 )
clear a ;
return ;
end
a = uint8(zeros(dlen,1)) ;
rd = double(dlen * 8) ;
rl = double(s(1)*s(2)-s(2)) ;
for i=2:s(1)
for j=1:s(2)
if rnd(i,j)<rd/rl
d = bitget (round(r(i,j)/p) ,1) ;
a = z_set_bit (a,rd,d) ;
rd = rd - 1 ;
end
rl = rl - 1 ;
end
end
Remember: a needs to be returned ALLWAYS!
The error is not in that specific line, but in the "whole" function itself.
Your problem is that Matlab thinks that a its not going to be created. And actually in some case it may not be created.
The following line in the beginning of your function should do the trick
a=0; % well, or a=NaN; or whatever you want to return
Additionally, don't clear a in if (dlen > 10000000 ).
Here is my code. The intent is I have a Wireshark capture saved to a particularly formatted text file. The MATLAB code is supposed to go through the Packets, dissect them for different protocols, and then make tables based on those protocols. I currently have this programmed for ETHERNET/IP/UDP/MODBUS. In this case, it creates a column in MBTable each time it encounters a new register value, and each time it comes across a change to that register value, it updates the value in that line of the table. The first column of MBTable is time, the registers start with the second column.
MBTable is preallocated to over 100,000 Rows (nol is very large), 10 columns before this code is executed. The actual data from a file I'm pulling into the table gets to about 10,000 rows and 4 columns and the code execution is so slow I have to stop it. The tic/toc value is calculated every 1000 rows and continues to increase exponentially with every iteration. It is a large loop, but I can't see where anything is growing in such a way that it would cause it to run slower with each iteration.
All variables get initialized up top (left out to lessen amount of code.
The variables eth, eth.ip, eth.ip.udp, and eth.ip.udp.modbus are all of type struct as is eth.header and eth.ip.header. WSID is a file ID from a .txt file opened earlier.
MBTable = zeros(nol,10);
tval = tic;
while not(feof(WSID))
packline = packline + 1;
fl = fl + 1;
%Get the next line from the file
MBLine = fgetl(WSID);
%Make sure line is not blank or short
if length(MBLine) >= 3
%Split the line into 1. Line no, 2. Data, 3. ASCII
%MBAll = strsplit(MBLine,' ');
%First line of new packet, if headers included
if strcmp(MBLine(1:3),'No.')
newpack = true;
newtime = false;
newdata = false;
stoppack = false;
packline = 1;
end
%If packet has headers, 2nd line contains timestamp
if newpack
Ordered = false;
if packline == 2;
newtime = true;
%MBstrs = strsplit(MBAll{2},' ');
packno = int32(str2double(MBLine(1:8)));
t = str2double(MBLine(9:20));
et = t - lastt;
if lastt > 0 && et > 0
L = L + 1;
MBTable(L,1) = t;
end
%newpack = false;
end
if packline > 3
dataline = int16(str2double(MBLine(1:4)));
packdata = strcat(packdata,MBLine(7:53));
end
end
else
%if t >= st
if packline > 3
stoppack = true;
newpack = false;
end
if stoppack
invalid = false;
%eth = struct;
eth.pack = packdata(~isspace(packdata));
eth.length = length(eth.pack);
%Dissect the packet data
eth.stbyte = 1;
eth.ebyte = eth.length;
eth.header.stbyte = 1;
eth.header.ebyte = 28;
%Ethernet Packet Data
eth.header.pack = eth.pack(eth.stbyte:eth.stbyte+27);
eth.header.dest = eth.header.pack(eth.header.stbyte:eth.header.stbyte + 11);
eth.header.src = eth.header.pack(eth.header.stbyte + 12:eth.header.stbyte + 23);
eth.typecode = eth.header.pack(eth.header.stbyte + 24:eth.header.ebyte);
if strcmp(eth.typecode,'0800')
eth.type = 'IP';
%eth.ip = struct;
%IP Packet Data
eth.ip.stbyte = eth.header.ebyte + 1;
eth.ip.ver = eth.pack(eth.ip.stbyte);
%IP Header length
eth.ip.header.length = 4*int8(str2double(eth.pack(eth.ip.stbyte+1)));
eth.ip.header.ebyte = eth.ip.stbyte + eth.ip.header.length - 1;
%Differentiated Services Field
eth.ip.DSF = eth.pack(eth.ip.stbyte + 2:eth.ip.stbyte + 3);
%Total IP Packet Length
eth.ip.length = hex2dec(eth.pack(eth.ip.stbyte+4:eth.ip.stbyte+7));
eth.ip.ebyte = eth.ip.stbyte + max(eth.ip.length,46) - 1;
eth.ip.pack = eth.pack(eth.ip.stbyte:eth.ip.ebyte);
eth.ip.ID = eth.pack(eth.ip.stbyte+8:eth.ip.stbyte+11);
eth.ip.flags = eth.pack(eth.ip.stbyte+12:eth.ip.stbyte+13);
eth.ip.fragoff = eth.pack(eth.ip.stbyte+14:eth.ip.stbyte+15);
%Time to Live
eth.ip.ttl = hex2dec(eth.pack(eth.ip.stbyte+16:eth.ip.stbyte+17));
eth.ip.typecode = eth.pack(eth.ip.stbyte+18:eth.ip.stbyte+19);
eth.ip.checksum = eth.pack(eth.ip.stbyte+20:eth.ip.stbyte+23);
%eth.ip.src = eth.pack(eth.ip.stbyte+24:eth.ip.stbyte+31);
eth.ip.src = ...
[num2str(hex2dec(eth.pack(eth.ip.stbyte+24:eth.ip.stbyte+25))),'.', ...
num2str(hex2dec(eth.pack(eth.ip.stbyte+26:eth.ip.stbyte+27))),'.', ...
num2str(hex2dec(eth.pack(eth.ip.stbyte+28:eth.ip.stbyte+29))),'.', ...
num2str(hex2dec(eth.pack(eth.ip.stbyte+30:eth.ip.stbyte+31)))];
eth.ip.dest = ...
[num2str(hex2dec(eth.pack(eth.ip.stbyte+32:eth.ip.stbyte+33))),'.', ...
num2str(hex2dec(eth.pack(eth.ip.stbyte+34:eth.ip.stbyte+35))),'.', ...
num2str(hex2dec(eth.pack(eth.ip.stbyte+36:eth.ip.stbyte+37))),'.', ...
num2str(hex2dec(eth.pack(eth.ip.stbyte+38:eth.ip.stbyte+39)))];
if strcmp(eth.ip.typecode,'11')
eth.ip.type = 'UDP';
eth.ip.udp.stbyte = eth.ip.stbyte + 40;
eth.ip.udp.src = hex2dec(eth.pack(eth.ip.udp.stbyte:eth.ip.udp.stbyte + 3));
eth.ip.udp.dest = hex2dec(eth.pack(eth.ip.udp.stbyte+4:eth.ip.udp.stbyte+7));
eth.ip.udp.length = hex2dec(eth.pack(eth.ip.udp.stbyte+8:eth.ip.udp.stbyte+11));
eth.ip.udp.checksum = eth.pack(eth.ip.udp.stbyte+12:eth.ip.udp.stbyte+15);
eth.ip.udp.protoID = eth.pack(eth.ip.udp.stbyte+20:eth.ip.udp.stbyte+23);
if strcmp(eth.ip.udp.protoID,'0000')
eth.ip.udp.proto = 'MODBUS';
%eth.ip.udp.modbus = struct;
eth.ip.udp.modbus.stbyte = eth.ip.udp.stbyte+16;
eth.ip.udp.modbus.transID = eth.pack(eth.ip.udp.modbus.stbyte:eth.ip.udp.modbus.stbyte+3);
eth.ip.udp.modbus.protoID = eth.ip.udp.protoID;
eth.ip.udp.modbus.length = int16(str2double(eth.pack(eth.ip.udp.modbus.stbyte + 8:eth.ip.udp.modbus.stbyte + 11)));
eth.ip.udp.modbus.UID = eth.pack(eth.ip.udp.modbus.stbyte + 12:eth.ip.udp.modbus.stbyte + 13);
eth.ip.udp.modbus.func = hex2dec(eth.pack(eth.ip.udp.modbus.stbyte + 14:eth.ip.udp.modbus.stbyte+15));
eth.ip.udp.modbus.register = eth.pack(eth.ip.udp.modbus.stbyte + 16: eth.ip.udp.modbus.stbyte+19);
%Number of words to a register, or the number of registers
eth.ip.udp.modbus.words = hex2dec(eth.pack(eth.ip.udp.modbus.stbyte+20:eth.ip.udp.modbus.stbyte+23));
eth.ip.udp.modbus.bytes = hex2dec(eth.pack(eth.ip.udp.modbus.stbyte+24:eth.ip.udp.modbus.stbyte+25));
eth.ip.udp.modbus.data = eth.pack(eth.ip.udp.modbus.stbyte + 26:eth.ip.udp.modbus.stbyte + 26 + 2*eth.ip.udp.modbus.bytes - 1);
%If func 16 or 23, loop through data/registers and add to table
if eth.ip.udp.modbus.func == 16 || eth.ip.udp.modbus.func == 23
stp = eth.ip.udp.modbus.bytes*2/eth.ip.udp.modbus.words;
for n = 1:stp:eth.ip.udp.modbus.bytes*2;
%Check for existence of register as a key?
if ~isKey(MBMap,eth.ip.udp.modbus.register)
MBCol = MBCol + 1;
MBMap(eth.ip.udp.modbus.register) = MBCol;
end
MBTable(L,MBCol) = hex2dec(eth.ip.udp.modbus.data(n:n+stp-1));
eth.ip.udp.modbus.register = dec2hex(hex2dec(eth.ip.udp.modbus.register)+1);
end
lastt = t;
end
%If func 4, make sure it is the response, then put
%data into table for register column
elseif false
%need code to handle serial to UDP conversion box
else
invalid = true;
end
else
invalid = true;
end
else
invalid = true;
end
if ~invalid
end
end
%end
end
%Display Progress
if int64(fl/1000)*1000 == fl
for x = 1:length(mess);
fprintf('\b');
end
%fprintf('Lines parsed: %i',fl);
mess = sprintf('Lines parsed: %i / %i',fl,nol);
fprintf('%s',mess);
%Check execution time - getting slower:
%%{
ext = toc(tval);
mess = sprintf('\nExecution Time: %f\n',ext);
fprintf('%s',mess);
%%}
end
end
ext = toc - exst;
Update: I updated my code above to remove the overloaded operators (disp and lt were replaced with mess and lastt)
Was asked to use the profiler, so I limited to 2000 lines in the table (added && L >=2000 to the while loop) to limit the execution time, and here are the top results from the profiler:
SGAS_Wireshark_Parser_v0p7_fulleth 1 57.110 s 9.714 s
Strcat 9187 29.271 s 13.598 s
Blanks 9187 15.673 s 15.673 s
Uigetfile 1 12.226 s 0.009 s
uitools\private\uigetputfile_helper 1 12.212 s 0.031 s
FileChooser.FileChooser>FileChooser.show 1 12.085 s 0.006s
...er>FileChooser.showPeerAndBlockMATLAB 1 12.056 s 0.001s
...nChooser>FileOpenChooser.doShowDialog 1 12.049 s 12.049 s
hex2dec 44924 2.944 s 2.702 s
num2str 16336 1.139 s 0.550 s
str2double 17356 1.025 s 1.025 s
int2str 16336 0.589 s 0.589 s
fgetl 17356 0.488 s 0.488 s
dec2hex 6126 0.304 s 0.304 s
fliplr 44924 0.242 s 0.242 s
It appears to be strcat calls that are doing it. I only explicitly call strcat on one line. Are some of the other string manipulations I'm doing calling strcat indirectly?
Each loop should be calling strcat the same number of times though, so I still don't understand why it takes longer and longer the more it runs...
also, hex2dec is called a lot, but is not really affecting the time.
But anyway, are there any other methods I can use the combine the strings?
Here is the issue:
The string (an char array in MATLAB) packdata was being resized and reallocated over and over again. That's what was slowing down this code. I did the following steps:
I eliminated the redundant variable packdata and now only use eth.pack.
I preallocated eth.pack and a couple "helper variables" of known lengths by running blanks ONCE for each before the loop ever starts
eth.pack = blanks(604);
thisline = blanks(47);
smline = blanks(32);
(Note: 604 is the maximum possible size of packdata based on headers + MODBUS protocol)
Then I created a pointer variable to point to the location of the last char written to packdata.
pptr = 1;
...
dataline = int16(str2double(MBLine(1:4)));
thisline = MBLine(7:53); %Always 47 characters
smline = [thisline(~isspace(thisline)),blanks(32-sum(~isspace(thisline)))]; %Always 32 Characters
eth.pack(pptr:pptr+31) = smline;
pptr = pptr + 32;
The above was inside the 'if packline > 3' block in place of the 'packdata =' statement, then at the end of the 'if stoppack' block was the reset statement:
pptr = 1; %Reset Pointer
FYI, not surprisingly this brought out other flaws in my code which I've mostly fixed but still need to finish. Not a big issue now as this loop executes lightning fast with these changes. Thanks to Yvon for helping point me in the right direction.
I kept thinking my huge table, MBTable was the issue... but it had nothing to do with it.
Hey guys, I have a very simple problem in MATLAB:
I have some strings which are like this:
Pic001
Pic002
Pic003
004
Not every string starts with the prefix "Pic". So how can I cut off the part "pic" that only the numbers at the end shall remain to have an equal format for all my strings?
Greets, poeschlorn
If 'Pic' only ever occurs as a prefix in your strings and nowhere else within the strings then you could use STRREP to remove it like this:
>> x = {'Pic001'; 'Pic002'; 'Pic003'; '004'}
x =
'Pic001'
'Pic002'
'Pic003'
'004'
>> x = strrep(x, 'Pic', '')
x =
'001'
'002'
'003'
'004'
If 'Pic' can occur elsewhere in your strings and you only want to remove it when it occurs as a prefix then use STRNCMP to compare the first three characters of your strings:
>> x = {'Pic001'; 'Pic002'; 'Pic003'; '004'}
x =
'Pic001'
'Pic002'
'Pic003'
'004'
>> for ii = find(strncmp(x, 'Pic', 3))'
x{ii}(1:3) = [];
end
>> x
x =
'001'
'002'
'003'
'004'
strings = {'Pic001'; 'Pic002'; 'Pic003'; '004'};
numbers = regexp(strings, '(PIC)?(\d*)','match');
for cc = 1:length(numbers);
fprintf('%s\n', char(numbers{cc}));
end;